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I had long been well-acquainted with the reputation of Mr. Cheng Yunlai. The year before last, he moved from Xiling and settled next door to me, allowing me to become even more familiar with the profundity of his academic attainments. Reading his commentary on *Jinkui Yufang* (Golden Cabinet Jade Chamber), I found it described as: "probing the source of the Yellow River in an ancient reservoir, and tracing the origin of mountains between Kunlun and Min." Furthermore, reading his *Jide Fang* (Immediate Acquisition Formula), it was likened to: "diverting the nine-bend stream into field ditches, enabling millet and sorghum to flourish luxuriantly, so that even a small ladle can scoop up water, thereby nourishing the world like abundant rain." Subsequently, he presented two volumes of *Yixia Zhiyan* (Casual Remarks on Medicine) to me, requesting a preface. After pondering over them for a long time, I came to understand that Mr. Cheng had deeply immersed himself in the study of human nature, life, and physical principles, and subsequently directed his interest toward medicine, achieving subtlety in all his endeavors; this text merely reveals one aspect of his mastery. People of the world equate physicians with shamans, historians, diviners, and priests, believing they follow a path separate from Confucian scholars. They do not realize that without understanding the principles of Heaven, Earth, and Humanity, one cannot discuss matters involving acupuncture and stone needles. How much less so those absurd practices? Moreover, this applies not only to physicians but also to shamans, historians, diviners, and priests. Shao Yaofu spent decades at Baiquan without using a furnace or fan, eventually composing the *Huangji Jingshi Guanwu Neiwai Pian* (Inner and Outer Chapters of Observing Things in the Supreme Ultimate Governing the World); people only knew him for his expertise in mathematics. Zhu Danxi studied the learning of mind and nature, receiving transmission from Master Xu of Baiyun. Because his teacher fell ill, he subsequently learned medicine, yet people still referred to him primarily as a physician. However, since the *History of Yuan* includes him in the Biographies of Daoist Scholars, we know that what will make Mr. Cheng Yunlai's legacy immortal is not solely his medical skills, but also the existence of *Zhiyan*. As Mr. Zhancheng beautifully wrote in his preface: "How can a physician have leisure? Yet which matter in the world is accomplished without leisure?" One need not mention the composure of wearing a silk headscarf and loose belt. When Wang Yangming faced days where arrows and stones flew across each other, he continued lecturing without ceasing. Even when battles slightly retreated, he would come out to distribute rewards and punishments, then return inside to explain previous lessons to his students, speaking without confusion. Was this not due to his leisure? Thus, he could achieve the merit of pacifying rebellion. However, without accumulating learning and understanding the Way, how could one remain calm and composed during moments of haste and urgency? Mr. Cheng is one who understands the Way, and by embedding this in medicine, the learning of human nature, life, and physical principles becomes visible. Is *Zhiyan* anything other than this? Furthermore, his family possesses a copy of Song Huizong's *Shengji Zonglu* (General Records of Sacred Healing). During the Dade era of the Yuan Dynasty, Yelü Chucai republished it, expanding it to over two hundred volumes, a version unseen in the world. He immerses himself day and night in such studies, naturally producing results beyond expectation. He then seeks words from me, humble as I am. Does he believe the Way resides in chaff and gravel? I merely offer this to fulfill his request, knowing full well I cannot imitate the steps of the son of Lifen while being blindfolded.
Written respectfully by my fellow student Xue Heng from Yuanshui, on Qingming Festival, Ding-Si Year of the Kangxi Reign.