On the eighth day of the twelfth lunar month in Cyan Ox Village, fine snow drifted down. Inside the Medicine Cottage, the stone mortar went "thud, thud." Zhang Yifan, however, was squatting by the stove tinkering with a strange-looking wooden frame: four jujube-wood pestles hung from the crossbeam, their heads wrapped in cotton-linen covers, and beneath them, beside the stone mortar, a spinning bamboo funnel had been installed. It was his newly improved "automatic rice cake pounding machine."
"What mischief is Brother Fan up to now?" Xiaoxiu barged in with her head covered in snow flakes, clutching a handful of stolen glutinous rice flour. "Uncle Wang says you're going to make the stone mortar dance by itself!"
Without raising his head, Zhang Yifan suddenly pulled a hemp rope. The pestle smashed into the stone mortar with a *swish*, splashing glutinous rice flour all over Xiaoxiu's face. "Watch closely. This is called 'leveragability'—using the heat from the stove to lift the wooden frame, and the pestles will rise and fall on their own, three times faster than your mother's rolling pin!"
Xiaoxiu sneezed as she wiped off the flour, then suddenly noticed a red string tied around the wooden frame, with a small bell dangling from the end. "What's this?"
"An anti-thief mechanism!" Zhang Yifan blinked. "Whoever dares to secretly grab the glutinous rice flour, the bell will ring and lure Old Cyan Ox over to butt them—just like last week when you sneaked to pick my winter plum blossoms and got chased by the cow for half a li."
Xiaoxiu instantly shrank his neck, then suddenly caught sight of half a roasted sweet potato exposed inside the stone mortar. He reached out to grab it, but the pestle gave his hand a *thud* of a rap.
"Little rascal!" Zhang Yifan laughed and scolded, rapping him on the head. Suddenly, he heard the "tap-tap" sound of a jujube-wood cane striking the floor coming from outside. The stem of the Old Daoist's pipe poked in through the crack of the door curtain. "Still using my glutinous rice for your experiments? Watch out for drinking the northwest wind tonight!"
Zhang Xuanzhen lifted the cotton curtain and saw the mess all over the floor, but when his cloudy eyes caught sight of the four trigrams of "Wind, Fire, Water, Mountain" carved onto the wooden frame, a faint glimmer flashed through them.
At noon, the Medicine Cottage was filled with the sweet fragrance of freshly made rice cakes. Zhang Xuanzhen bit into a rice cake handed to him by Xiaoxiu and suddenly spoke, "Yifan, what is the Dao?"
The boy wiped the glutinous rice flour off the pestle, gazing at the flickering charcoal fire in the stove. "The Dao is right here in this rice cake. Look, the glutinous rice needs to soak for seven hours (fire generates earth); the pestles must fall thirty-nine times (aligning with the number of seven-seven); the cotton-linen covers are wrapped three times (representing the three powers of heaven, earth, and mankind)—even when Xiaoxiu steals the flour and the bell rings five times (responding to the five elements), it is all the Dao."
The Old Daoist suddenly choked on a puff of smoke, coughing as he laughed and scolded, "What a clever twisting of logic! Turning the Book of Changes into a rice cake manual—quite fitting, though."
He suddenly fished out half an old silk painting from his bosom and unfolded it to reveal the Chang'an Market Map, its ink lines concealing Qimen Dunjia directional coordinates. "Tomorrow, accompany me to town to trade for New Year goods, and bring this map along—it's time you saw the wider world."
Zhang Yifan's hand trembled, and the pestle dropped to the ground with a *clatter*. Xiaoxiu was busy boiling sugar syrup by the stove; hearing this, he flustered so badly that the syrup almost spilled onto his apron. Seizing the opportunity, Xiaoxiu grabbed a piece of rice cake, shoved it into his mouth, and shouted indistinctly, "Brother Fan is going to Chang'an City? Then who is going to fix my spring-loaded wooden clogs when they break?"
As dusk crept into the Medicine Cottage, Zhang Xuanzhen sat on the millstone smoking his dry tobacco, watching his disciple squat on the threshold polishing abacus beads—an abacus he had carved from locust wood, its beads detachable for use as hidden projectiles.
"Remember when I found you ten years ago, and the Taiji Jade Pendant in your swaddling clothes?" The Old Daoist spoke abruptly. "The 'Taichu' at your waist, paired with my 'Taisu' here, is precisely the token of the Taiji Chamber of Commerce. Back then, the supreme leader and I agreed that whenever the jade pendant reappeared, it would be the day the Chamber of Commerce rose again."
The boy's fingertips grazed the warm jade pendant, suddenly recalling the caravan he had encountered being raided at the mountain temple, and the driver Uncle Wang's hesitant, unsaid expression. Snow grains pelted the paper window with a rustling sound. Xiaoxiu walked in holding a newly sewn cotton robe, and a sachet embroidered with a cyan ox tumbled out of the hem.
"Here you are. It's stuffed with herbs to ward off snakes and bugs, plus some chestnuts I've saved up..." Before he could finish speaking, he turned and ran off, blushing.
That night, Zhang Yifan lay on the pile of firewood reading the Classic of Hundred Insects when Xiaoxiu suddenly poked his head through the attic skylight, shoving something hard into his arms—it turned out to be a wooden plaque carved with the words "Made by Xiaoxiu," featuring a crudely drawn Wooden Ox Pestle.
"If people in Chang'an City bully you, just flash this wooden plaque!" Xiaoxiu lowered his voice. "I'll have all the dogs in the village go bite them!"
The snowlight reflected off the paper windows of the Medicine Cottage, casting two figures onto the frost-patterned glass. Zhang Xuanzhen gazed at the Wooden Ox Pestle model, the bamboo ventilation fan blueprints, and the cyan ox sachet sent by Xiaoxiu arrayed by his disciple's bedside, and suddenly understood that this child had long since fused the "Dao" into every calculation—calculating how to make the rice cakes sweeter, the mechanisms more ingenious, and the people around him warmer.
When the first crow of the rooster sounded, Zhang Yifan touched the jade pendant at his waist and got up, seeing his master stuffing seven colorful seeds into his bamboo basket—"Cyan Ox Seven," capable of adapting to northern and southern climates.
The Old Daoist coughed and turned around. "Don't sit there weeping and wailing like Xiaoxiu. The West Market in Chang'an City is a hundred times livelier than the threshing floor in Cyan Ox Village."
The boy suddenly gave a light laugh, tucking the abacus into his belt. "Master, rest assured. I will certainly let those Chang'an merchants know that the rice cake machine from Cyan Ox Village can also calculate the commercial pathways of the entire realm."
The snow had stopped, and the old locust tree outside the Medicine Cottage was draped in icicles, gleaming in the morning light. Xiaoxiu chased after him, shoving a roasted sweet potato into his pocket. Xiaoxiu waved a willow branch and shouted, "Come back soon!" while Old Cyan Ox let out a low "moo" from its pen.
With his bamboo basket on his back, Zhang Yifan stepped onto the stone slab path. The Taiji Jade Pendant at his waist resonated from afar with his master's "Taisu," and every step he took seemed like a trigram drawn in the snow—this trigram was Li, fire, the path of worldly immersion he was about to ignite.
The mountain wind swept past the bamboo water flume, emitting a crisp and clear sound, as if recounting some ancient prophecy. And the story of Cyan Ox Village would ultimately, alongside this boy carrying an abacus and holding the fragrance of rice cakes, gradually unfold into a magnificent epic concerning the "Dao within the Mortal World."