At the height of the cicadas' shrill song during noon, the Medicine Cottage was filled with the fragrance of newly baked wheat cakes. Zhang Yifan squatted in front of the stove, poking at the hearth fire and burying a purple sweet potato into the glowing red pile of coals. Suddenly, he heard the "tap-tap" sound of a jujube-wood walking stick striking the floor behind him. The old Daoist's pipe bowl swayed above his head, casting rings of pale blue smoke.
"Yifan, it's time to hand in your homework." Zhang Xuanzhen spoke abruptly, startling the boy so much that his hand jerked, sending soot flying all over his face. Huwa hid behind the door and snickered, while Xiaoxiu pressed her lips together in a smile as she held a freshly steamed wheat cake. Seeing Zhang Yifan's soot-smudged face, she almost dropped the porcelain plate to the floor.
"Master is testing me again?" Zhang Yifan fished out the oil-dripping roasted purple sweet potato, broke it in half, and handed it over. The charred aroma mingled with the sweet richness of the wheat cake, spreading through the summer heat. "Just yesterday, I demonstrated 'Ants Moving a Mountain' to Huwa—using sugar cubes to set up an Eight Trigrams Formation and letting them find their own way. It's even more miraculous than the Qimen Dunjia you taught me!"
The old Daoist took a bite of the purple sweet potato, hissing from the heat, but deliberately put on a stern face. "Don't try to fob me off with children's playthings! Zhuangzi said, 'Dao in Ants.' Tell me then, aren't the charcoal in this hearth, the steam from the steamed cakes, and the aroma of the roasted potato all manifestations of the Dao?" He suddenly tapped the stove with his pipe bowl. "Take this stove fire as your topic. If you can't answer, you'll be guarding the cowpen tonight."
The boy wiped his face and looked at the dancing flames, suddenly smiling. He picked up a thin piece of firewood and drew a crooked Taiji diagram in the charcoal ash. "Master, look here: when the fire burns fiercely, adding damp wood makes the smoke rise to drive away mosquitoes—that's 'dryness overcoming dampness.' When the fire burns too wildly, scattering some wheat bran makes the sparks jump up like stars, yet it allows the sweet potato to be crispy on the outside and tender on the inside—isn't that 'combining firmness and flexibility'?" He suddenly pointed at the medicine bundles hanging from the rafters. "The angelica you dry loves to absorb moisture, so I nailed a bamboo rack next to the stove, letting the medicinal vapors rise with the heat. It's thirty percent faster than the earth method you used last year!"
Xiaoxiu suddenly burst into a giggle. "Brother Fan is secretly modifying Master's medicine racks again! Last week, he even hung Huwa's cricket cage right under the astragalus, saying 'insect sounds can awaken the medicinal qi,' and ended up making all the crickets roll their eyes from the smoke!" Huwa immediately chimed in, "Exactly! My 'Golden Voice' almost turned into a 'Hoarse Voice'!"
Zhang Xuanzhen did not smile, however. His cloudy eyes stared at the Taiji diagram in the charcoal ash, his pipe bowl motionless for a long time. For ten years, this child had always loved transforming the "mutual generation of Yin and Yang" from the Taoist classics into the trivialities of the hearth: watering herbs with rice-washing water (water nourishing wood), using dried orange peels to kindle the fire (fire generating earth), and even dividing the fodder for the cyan ox into "spring shoots," "summer grass," "autumn fruits," and "winter roots" according to the seasons—clearly boiling down the five phases and six climatic factors of the Huangdi Neijing into the sweet, sour, bitter, and pungent flavors of everyday life.
"Deeper," the old Daoist said suddenly, his voice as light as a spark from the stove. "The Dao is in the stove fire, but where then is the Dao?"
Zhang Yifan turned serious, pulling the thumb-worn Classic of Hundred Insects from his tunic and turning to the page depicting ants moving sugar. "The Dao is when Huwa stole a cake, and I mixed deworming mugwort powder into the wheat cake—he ate it with relish, but the pests dared not come near. The Dao is when Xiaoxiu does her needlework, and I taught her to hide peppermint juice in the stitches so mice flee when they smell it. The Dao is when you brew medicine, deliberately mixing 'rushing fire' and 'slow fire' to force me to test and make mistakes myself." He suddenly raised his head, his eyes reflecting the dancing firelight. "Zhuangzi said, 'Dao in excrement and urine.' In truth, the Dao is right here beside this hearth, next to the medicine grinder, in everyone's calculations for daily living—calculating how to make bitter medicine sweet, how to bring water to dry fields, and how to make life like this roasted purple sweet potato: crispy on the outside, tender on the inside, with sweetness in the heart."
The old Daoist's pipe bowl clattered to the ground, startling the dozing sparrows on the rafters. Xiaoxiu and Huwa looked at each other in dismay, wondering why Grandfather Zhang, usually so stern, suddenly had red-rimmed eyes. After a long silence, the old Daoist slowly bent down to pick up his pipe, his voice carrying an imperceptible tremor. "A fine 'calculation for daily living'... Back then, Laozi rode the cyan ox out of the Hangu Pass and left behind five thousand words, yet they fall short of this practical truth of yours."
He suddenly turned and looked out the window. The bamboo tubes in the terraced fields gleamed silver in the sunlight, and the chirping of the Spring-Guiding Insects blended with the cicadas' song to weave a summer melody. The snowy night of ten years ago seemed right before his eyes; the infant in swaddling clothes could now comprehend the Dao from the stove fire, while the "Dao-medicine heritage" he had steadfastly guarded had never been about esoteric mysteries in ancient texts, but rather like the child's roasted purple sweet potato—down-to-earth, heartwarming, and carrying the earthy wisdom of human life.
"Accompany me into the mountains tomorrow," the old Daoist said abruptly, wiping the corner of his eye with his back to the boy. "We'll gather some 'spirit-awakening herb,' and by the way, hang your 'insect-sound clock' at the entrance of the village—let the villagers know that the Dao of our Cyan Ox Village is not up in the clouds, but right here in the stove fire and under everyone's hands."
Zhang Yifan was stunned, then saw Xiaoxiu make a funny face at him, while Huwa was secretly stuffing a scorched wheat cake into his pocket. The heat from the hearth washed over his face, mixed with the sweet fragrance of the purple sweet potato, and he broke into a grin. "Does Master mean I don't have to guard the cowpen tonight? Then how about teaching Huwa how to make an 'automatic fan' tonight? Using bamboo tubes to catch mountain springs to drive a paddle wheel will be ten times faster than his mother's cattail fan!"
The old Daoist laughed and scolded him, swinging his walking stick, but gently swerved it as it touched the boy's shoulder. "First finish completing your Classic of Hundred Insects! Last time you said 'fireflies can guide the way,' and as a result, Huwa followed them straight into a wolf den. If not for my cyan ox's sense of smell, he would have long since become wolf dung!" Huwa immediately shrank his neck, and Xiaoxiu laughed so hard her wheat cake dropped to the floor, causing the tabby cat in the kitchen to pounce with a "meow."
As twilight drifted into the Medicine Cottage, Zhang Yifan leaned over the windowsill to finish drawing the habits of fireflies, while Xiaoxiu stood beside him grinding pine soot ink. In the distance came Huwa's startled cry, "Brother Fan! Your 'automatic fan' blew all the drying medicinal herbs away!" The boy dropped his writing brush and dashed outside, his robe hem brushing the Classic of Hundred Insects off the table and revealing half a roasted purple sweet potato tucked between the pages—the "Dao Heart" Xiaoxiu had secretly slipped to him.
The old Daoist watched his disciple's retreating figure vanish into the twilight and let out a soft chuckle. The stove fire still danced, sparks leaping up and falling back down, just like these ten years of time—seemingly trivial, yet unwittingly boiling down the "Dao" into a tangible, touchable, and tasteable supreme flavor of the mortal world. Perhaps this was true transmission—not a condescending gaze from high above, but squatting beside the hearth, stewing the wisdom of human life with the warmth of cooking smoke.
When the first star lit up, the "insect-sound clock" outside the Medicine Cottage suddenly rang out, the chirping of the Spring-Guiding Insects mingling with the sound of water flowing through the bamboo tubes to play the nocturne of Cyan Ox Village. Zhang Xuanzhen stroked the Taiji Jade Pendant at his waist, suddenly realizing that the Dao belonging to Zhang Yifan had already planted its seed in these ten years of hearth fires, insect songs, and laughter, waiting only for the wind and rain of the mortal world to arrive before breaking through the soil and growing into his very own towering Dao.