The news that Xiaoyao Tower was being prepared spread throughout Chang’an, and many people thought Du Heng would immediately hire craftsmen to renovate the storefront, carve beams and paint rafters, and make the restaurant look magnificently imposing.
But to everyone’s surprise, he gathered the 10 craftsmen sent by the Ministry of Works in his own courtyard, without even having time to lay a single brick on the restaurant’s foundation.
The morning sunlight fell across the ridges between fields, carrying the moist scent of dew.
Du Heng stood before the craftsmen with a clear, powerful voice, his sleeves still stained with fresh dew and soil from the vegetable garden, and he had none of the airs of a “future restaurant keeper” as he said, “Masters, Your Majesty granted me the name ‘gewu’ not for me to show off my skills, but in the hope that I can use these abilities to benefit the common people. Today, I want to try 3 things together with all of you… if they work, they can help ordinary folk save a lot of effort in the future and suffer much less.”
The craftsmen looked at one another, their faces full of confusion.
They had originally thought they were ordered here to build a restaurant… nothing more than laying bricks and tiling roofs, planing doors and windows, and carving decorations… so how did they end up in Dujiawa, dragged to the edge of a vegetable plot to listen to a half-grown youth talk about “saving effort”?
One gray-haired old craftsman could not help muttering under his breath, “Building a restaurant is building a restaurant; can all this strange stuff put food on the table?”
Du Heng seemed not to hear everyone’s comments, and he did not explain either, but turned around and carried things out from the shed beside him, preparing to demonstrate.
The first thing was a pulley water-lifting device.
He first took out a thick hemp rope he had prepared long ago, a smoothly polished hardwood wheel, and a sturdy iron axle, and set up a simple pulley system between 2 trees in the courtyard.
He threaded the iron axle through the center of the hardwood wheel and fixed it onto a crossbeam between the 2 trunks, looped the thick hemp rope around the wooden wheel, tied an empty clay bucket to one end, and let the other end hang to the ground for people to pull.
The whole device looked simple, yet every part fit perfectly, and even the wheel’s axle hub was coated with lubricant he made by mixing beeswax and vegetable oil, so it turned without making a sound.
“Masters, watch closely.”
After Du Heng finished speaking, he signaled for the old craftsman who had muttered earlier to come over and try pulling the rope.
The old craftsman walked over, half believing and half doubting, still thinking to himself, how could a broken wooden wheel like this not take a huge amount of effort to lift a bucket of water?
But the moment he gave the rope a light tug, he froze… the clay bucket climbed steadily along the rope with no effort at all, as if he were lifting an empty basket.
He hurried to the water storage pond, filled the clay bucket with water, and tried pulling the rope again.
Although the full bucket was much heavier, it still lifted easily, rising steadily into midair without spilling a single drop.
“It saves effort! It saves so much effort… at least 3 times the effort!”
The old craftsman’s voice trembled with excitement as he pulled the rope back and forth and tried it several more times, his eyes full of disbelief, saying, “This old man has drawn water from wells for 30 years, fetching water for people every day, and I’ve never seen such a clever method! Before, pulling up 1 bucket would make my arms ache for ages, but like this, even the old women in the village can pull it up with ease!”
Du Heng smiled and nodded as he said, “If this pulley system is used by the well platform, the canal transport docks, or in mines, then whether old, weak, women, or children, anyone can draw water and move things easily. Water is the foundation of common people’s lives, and effort should be spent where it matters, not wasted on these repetitive, exhausting jobs.”
The second thing was a lever rice-pounding machine, and Du Heng named it “foot-treadle pounder.”
He found a thick, long hardwood beam to use as a lever, found a balance point in the middle, piled up a fulcrum with stones and mud, and set the wooden beam on top.
He tied a heavy stone mortar to one end of the beam for pounding grain, and fastened a thick wooden plank to the other end as a treadboard for people to step on.
Once everything was ready, Du Heng stood on it himself, and with a light step on the treadboard, the stone mortar on the other end rose; when he relaxed his foot, the stone mortar dropped heavily with a “thump,” pounding the grain in the stone trough below with a rustling sound.
The entire process kept an even rhythm and steady force, without taking any effort at all.
“With this ‘foot-treadle pounder,’ you can pound at least 100 jin of rice in a day, more than 10 times faster than hand-pounding.”
Du Heng demonstrated as he explained to the craftsmen, saying, “If every household in the village can use this, then women won’t have to bend over pounding rice every day until their waists break down, and children won’t have to help pound rice either, so they can go to school earlier to study.”
A young craftsman had already been itching to try, and before Du Heng even finished speaking, he jumped onto the treadboard impatiently and started stepping in Du Heng’s manner.
The stone mortar rose and fell with his movements, and before long, the grain in the stone trough shed its husks and revealed white rice kernels.
“This is so easy to use!” the young craftsman said excitedly.
“My wife pounds rice at home every day, and she has to stay busy until midnight before she can rest, and her waist gets so exhausted she can’t even straighten up, and she often cries out in pain! If we had a foot-treadle pounder like this, she would have it so much easier!”
As he spoke, his eyes reddened, clearly thinking of how hard his wife’s days usually were.
The third thing was the prototype of a light-focusing fire-starting “Sun Stove.”
Du Heng carried over a copper basin, whose inner wall he had polished until it shone like a mirror and clearly reflected people’s figures.
He aimed the copper basin at the sun in the sky, adjusted its angle to focus the sunlight onto a single point, and then placed a small pinch of dried mugwort tinder at the focal point.
Before long, sunlight broke through the clouds and landed right on the basin’s focus.
The mugwort tinder first let out a wisp of bluish smoke, then tiny sparks jumped out, and with a gentle blow, the flame whooshed to life, its dancing flicker warming everyone’s faces.
“Using this copper basin to focus light, you can start a fire anytime on a clear day, and you don’t need flint or a fire starter at all,” Du Heng said as he used the burning mugwort tinder to light the firewood beside him.
“If this method is used in the army, soldiers cooking in the wild won’t have to worry about having no fire; and villagers in the mountains heating themselves in winter can save a lot of firewood, and it can also prevent reckless tree-cutting and protect the forests.”
After the 3 demonstrations, the courtyard fell silent, so quiet that even the sound of wind passing through leaves could be heard clearly.
Some craftsmen gathered around the pulley system and gently turned the wooden wheel with their hands; some stepped on the foot-treadle pounder treadboard to savor the joy of saving effort; and others squatted beside the copper basin, staring at where the sunlight focused, their eyes glittering with excitement.
“Little young master… no, young master Du!”
The old craftsman walked forward excitedly and cupped his hands in salute to Du Heng, his tone deeply respectful as he said, “This isn’t witchcraft at all; this is the true ‘principles of gezhi’! This old one has forged iron for 40 years, and only today did I learn that strength can be used like this, and that fire can be borrowed from the sun in the sky! I truly lived in vain before!”
Du Heng hurried to return the salute, and he said solemnly, “The principle of gewu is not how novel and ingenious it is, but whether it is practical; it is not how dazzling and pretty it looks, but whether it can let everyone benefit. If all of you masters are willing, then in the future we can research these things together, make them even better, promote them to more places, do more real work for the country and the common people, and let everyone live a better life.”
“We’re willing! We’re willing!”
The craftsmen answered in unison, their voices loud and full of drive, and their earlier doubts about Du Heng had long turned into deep admiration.
The news quickly reached Chang’an, and Li Shimin was especially delighted after hearing it.
He personally wrote the 4 large characters “principles of gewu,” and also sent envoys to deliver 10 bolts of fine silk to Dujiawa, and he ordered the Directorate of Imperial Works to record the diagrams of the pulleys and levers and to try them first at canal transport docks and granaries near the capital to see the results.
But Du Heng exchanged all the rewarded silk for iron materials, copper mirrors, and hemp rope.
He said, “Silk is fine, but it can’t be used to make tools, and with these iron materials, we can make more pulleys and foot-treadle pounders so that more people can use these good things.”
Over the next few days, he lay at his desk every day drawing new diagrams, producing a compound pulley system… more effort-saving than the previous single pulley system, usable for hoisting heavy building materials, saving at least 5 times the effort; a water-powered rice pounder… no need for people to step on it, because it used mountain spring water’s strength to drive a wooden wheel, pounding rice day and night with higher efficiency; and a curved-surface concentrating stove… changing the copper basin into a curved surface for better concentrating, so on clear days you could boil water and cook with it without burning firewood.
He understood clearly in his heart that promoting these new technologies had to be done step by step, and he could not rush.
He needed to start with simple devices so everyone could see the benefits and build trust, and then slowly research more complex systems to raise efficiency.
He would first trial them in a small village like Dujiawa, discover problems and improve them, then promote them to prefectures and counties, and finally popularize them nationwide.
One day, Princess Changle came to Dujiawa again.
She did not wear gorgeous palace attire, and only draped herself in a plain-colored cloak, looking like an ordinary noble young lady.
As soon as she entered the courtyard, she saw the craftsmen tuning a newly made water-powered rice pounder… mountain spring water flowed in along a dug channel, drove the wooden wheel below to turn, and the wooden wheel in turn moved the lever above so the stone mortar rose and fell automatically, the “thump-thump” sounding rhythmic like drumming, while a faint scent of rice drifted through the air.
“If this water-powered rice pounder can be promoted to every prefecture and county, the common people can save at least half a day every day, cultivate 1 more mu of land, and harvest a lot more grain.”
Princess Changle spoke softly, her eyes holding both admiration for the invention and contemplation of the future.
Du Heng nodded in agreement as he said, “But when promoting it, we need unified standards, or else every place will make it differently, and it will break easily and be hard to repair. I plan to compile a book called Gewu Device Construction Register, with detailed diagrams, and I’ll write everything clearly… each part’s measurements, what material to use, and how to assemble it. When the time comes, craftsmen can build from the diagrams, and ordinary folk can repair it by following the register, and only then can it truly be popularized.”
A gleam flashed in Princess Changle’s eyes, and her gaze at Du Heng was full of appreciation as she said, “You not only know how to make things, you also understand how to set rules… this is the beginning of building institutions. If the art of gewu has no unified standards, then even the best inventions are only novel little toys; but once there are regulations, they can become sharp tools that are useful to the country and the people.”
She suddenly leaned close to Du Heng, her voice as light as a breeze, almost audible only to the two of them as she said, “Father Emperor has already had Lord Wei Zheng investigate Zhangsun Chong’s character. If any misconduct is found, then my engagement to him can be annulled.”
Du Heng’s heart jolted, and the wooden ruler in his hand nearly fell to the ground.
He quickly steadied himself and looked at Princess Changle seriously as he said, “Princess, you don’t need to take risks for my sake. I am walking the path of gewu, and even without an engagement, I will keep walking it. If our private feelings affect your reputation, then it will instead violate my original intent of promoting gewu and benefiting the common people.”
Princess Changle gazed at him, her eyes as clear as autumn waters reflecting the bright moon, and she spoke with firm resolve, saying, “But I am willing to walk this road with you. It is not because of romantic feelings between man and woman, but for the Great Dao in my heart. You light the stove-fire of gewu, and I will help you guard that flame and not let the wind blow it out; you draw the diagrams for promotion, and I will help you clear the court’s policies so more people support you. This is our shared undertaking, not my one-sided wish.”
When she was about to leave, Princess Changle left behind the plaque inscribed with “principles of gewu” in Li Shimin’s own hand, and she personally helped Du Heng hang it above the courtyard gate.
The 4 characters on the plaque gleamed under the sunlight, exceptionally eye-catching.
After seeing the plaque, the villagers no longer dared to casually call him “Du Xiaolang” as before, and every time they saw Du Heng, they respectfully addressed him as “Du gewu.”
When the village children passed by the courtyard gate, they would also stop, tilt up their little faces to look at the plaque, their eyes full of longing as they softly murmured, “I’m going to learn gewu in the future too, just like young master Du, and make good things that help everyone save effort!”
Du Heng stood beneath the plaque and looked in Chang’an’s direction, the corners of his mouth lifting slightly.
He knew that pulleys and levers were only the beginning, and that many more inventions awaited his exploration… making light-transmitting mirrors out of glass so the concentrating effect would be better; purifying saltpeter to make ice so food could keep longer in summer; using Qunie ferment to make medicinal herbs to treat more illnesses; and even using steam’s strength to push carts, making transport easier… and the true long scroll of gewu had only just begun to unfurl.
The stove-fire in the courtyard had not yet gone out, and the craftsmen’s “clang-clang” of toolmaking had already rung out.
Du Heng knew that his half-mu wasteland courtyard would one day become the cradle of Great Tang industrial civilization… here, there was no reliance on destiny and no dependence on pedigree, only pairs of diligent hands and rational minds, lighting a lamp that could illuminate the lives of countless common people.
And that lamp’s spark, besides his own never-extinguished faith in “gewu for practical use, benefiting the state and the people,” also included the jar of “rose chili sauce” Princess Changle quietly pressed into his hands… the heat of the chili sauce was like the challenges on the road of gewu, and the fragrance of the rose was like the smiles when the people benefited, urging him at every moment to keep moving forward step by step with resolve.