Autumn on Cyan Ox Ridge looked like an overturned paint can, with golden rice drying in the threshing ground. Zhang Yifan, however, squatted beneath the old locust tree, staring blankly at a half-cut bamboo tube. Huwa walked over holding a freshly picked wild persimmon, juice dripping down between his fingers. "Is Brother Fan acting silly again? Uncle Wang's rice-husking mortar already has three cracks, and you still have the mind to watch ants?"
The boy suddenly raised his head, a sharp gleam flashing in his eyes. "Precisely because the mortar is cracked, we need to build a 'Wooden Ox Pestle'!" He pulled out a sharply whittled mulberry branch and began sketching a mechanism on the ground. "Using the principle of the repeating crossbow from Mozi, we connect the bamboo tubes to the waterwheel wheel. The flowing water drives the gears, and the gears connect to the husking mallet. It'll be ten times faster than human labor!" Huwa looked as though he half-understood, then suddenly pointed at the drawn ox head and laughed, "Brother Fan is scribbling wildly again. A gear growing out of a cow's head makes it look like an iron-headed monster!"
Three days later, a strange-looking wooden frame stood by Cyan Ox Creek: a four-foot-tall wooden ox raised its head, its mouth wide open, its tongue a pestle made of jujube wood as thick as a bowl. Hidden inside the ox's belly were seven sets of gears, driven entirely by mountain springs channeled from the upper reaches through bamboo tubes. Zhang Yifan stood beside the wooden ox, clutching a halter rope tied with a bronze bell, looking just like he was leading a real ox.
"Time to husk!" Huwa waved a willow branch and shouted. Villagers crowded around carrying harvested rice, while Hunter Li stroked the mortise and tenon joints on the wooden ox and shook his head repeatedly. "The brat is just messing around. If this contraption falls apart, I'm afraid it'll churn the creek water to mud." Zhang Yifan, unruffled, poured half a dou of rice into the ox's mouth and pulled the halter. Amidst the rushing "swish-swish" of the mountain spring striking the waterwheel, the pestle went "thud, thud" into the stone mortar. As rice husks flew, pearly white grains bounced into the bamboo sieve, leaving the onlookers dumbfounded.
"It really worked!" Huwa's mother picked up a grain of rice and exclaimed, "It's even more evenly milled than my man does!" Taking the opportunity, Zhang Yifan pulled out a small notebook. "Auntie, remember this: using this Wooden Ox Pestle to mill rice, for every dou of rice, half a sheng of rice will be collected as a 'machining fee'. Once we save up ten dou, we can buy Huwa a new writing brush—so he stops stealing my wolf-hair brushes." Huwa immediately hid behind Hunter Li, drawing roars of laughter from the crowd.
Just as everyone was praising it, the wooden ox suddenly let out a strange creak, its pestle tilting to one side and almost hitting Huwa. Zhang Yifan quick as lightning grabbed the halter, only to find a locust leaf jammed between the gears—Huwa had taken advantage of his inattention to stuff a handful of locust flowers into the wooden ox's mouth. "You little rascal!" The boy chased Huwa across the threshing ground, the hem of his robe sweeping away the rice grains in the bamboo sieve. Xiaoxiu smiled as she squatted down to pick them up, then suddenly noticed two pieces of mica embedded in the wooden ox's eyes, blinking in the sunlight as if rolling its eyes.
At noon, the Medicine Cottage was filled with the fragrance of newly cooked rice. Zhang Xuanzhen tasted the porridge cooked by Xiaoxiu, then suddenly pointed at the wooden ox and asked, "Why carve insect patterns on the gears?" Zhang Yifan wiped his sweat and smiled, "I carved patterns of 'strength beetles'. They can carry things ten times heavier than themselves, just borrowing a lucky omen."
The old Daoist suddenly set down his bowl, his tobacco pouch tapping three crisp strikes against the table. "Observing the stars last night, the Ziwei Star shifted, signaling the emergence of a guiding star—Yifan, do you know that this Wooden Ox Pestle is more than just a tool for husking rice?"
The boy froze, gazing at the busy wooden ox outside the window, and suddenly understood. "The Wooden Ox Pestle is a primer. What it entices is the villagers' belief that 'new methods can lead to a good life.' Just like Master used a cyan ox calf to plow the fields back then, making everyone believe that 'animal power surpasses human labor.' Today, I use the Wooden Ox Pestle to make everyone believe that 'mechanisms surpass brute force.'" He lowered his head slightly, his voice softening. "Actually, I want even more for everyone to know that the knowledge in books is not just for display; it can turn into grains of rice, into ironware, into a good life."
The old Daoist chuckled softly, a faint light flickering in his cloudy eyes. He remembered ten years ago, when he used half a jade pendant to persuade the villagers to take in Zhang Yifan. Now, his disciple used a Wooden Ox Pestle to make the villagers believe that "reading changes lives." Perhaps this was the transmission of the "Dao"—from the cyan ox calf to the Wooden Ox Pestle, from the swaddling clothes in the snow to the laughter on the threshing ground, every object was a key unlocking human hearts.
When twilight crept across the threshing ground, the Wooden Ox Pestle was still going "thud, thud." Villagers lined up waiting to husk rice, and Huwa brandished a willow branch to "shoo flies" away from the wooden ox, looking like a little cowherd. Zhang Yifan squatted beside the wooden ox to adjust the gears, and Xiaoxiu walked over carrying a newly sewn ox-shaped cloth bag filled with dried strength beetle shells. "Here. You said these shells could reinforce the gears; I've saved up half a basketful."
The boy took the cloth bag, suddenly noticing the crooked gear patterns embroidered on it, and couldn't help smiling. "Xiaoxiu's needlework has improved; it's ten times better than Huwa's drawings." The girl blushed and turned away, only to hear him muttering behind her, "Once we save enough money, I should get the wooden ox a pair of bronze gears, and by the way, make Huwa a kite that can fly—styled just like the 'wooden kite' in Mozi."
That night, Zhang Xuanzhen sat on the doorstep smoking his dry tobacco, watching his disciple record in the "Book of Mechanisms" beside the wooden ox. As the tip of the brush glided past "the ratio of waterwheel rotational speed to pestle force," he spoke up. "Tomorrow, come with me to town to trade for salt, and bring the blueprints of the Wooden Ox Pestle along—perhaps the artisans in Chang'an City will drop their jaws when they see them."
Zhang Yifan looked up and saw the Taiji Jade Pendant at his master's waist gleaming faintly in the moonlight, suddenly recalling what Huwa's mother had said about the "Ziwei Star shifting." Mountain wind swept across the threshing ground, and the shadow of the Wooden Ox Pestle swayed on the ground like a real cyan ox, stepping through the moonlight toward a broader world. Perhaps the "Dao" belonging to him was hidden right here within the wooden ox's gears, tucked away in the villagers' smile lines, embedded in every calculation that turned book learning into daily life.
When the first star lit up, a startled cry from Huwa rang out across the threshing ground: "Brother Fan! The wooden ox swallowed my persimmon!" The boy ran over with a smile, only to find Huwa peering into the wooden ox's mouth, still clutching half an unfinished persimmon cake in his hand. Under the moonlight, the wooden ox's mica eyes blinked and blinked, almost as if it were holding back a laugh—this, perhaps, was the "Dao" in Zhang Yifan's eyes: carrying the earthy warmth of the mortal world, hidden within every mischievous calculation, making bitter days sweet and breathing life into dead knowledge.