Conventional historiography of East Asian medicine relates that the medical fundamentals were already established by the ancient sages and that the history of East Asian medicine is about the processes of illuminating the ancients’ profound wisdom believed to have been prefigured in the classical texts. In this respect, this paper draws attention to the treatise “On the Origin of Medicine” (醫源論) of the Eastern Medicine [for] Prolonging the World and Preserving People (東醫壽世保元), authored by YI Jema 李濟馬 (1837-1900) in late Joseon Korea. YI Jema viewed the history of (presumably East Asian) medicine, not as the process of substantiating the Way Orthodoxy (道統), but rather as that of accumulating medico-pharmaceutical experiences (醫藥經驗) such as disease patterns and medication dynamics (病證藥理), thus making it open to analytic investigations yet to come. Through this historicizing process, YI Jema was able to interpret, reconfigure, and synthesize the inherited tradition of East Asian medicine, pushing it forward beyond where it had been before. This historical event makes an illustrative example of the East Asian medicine being diverse and dynamic as against the conventional understanding. His medical outlook, by implication, went beyond the so-called “center-periphery” frames, China vs. Joseon, Confucianism vs. medicine, and text vs. experience.