Daoism is a very important subject that consists of oriental medicine(traditional east asia medicine). Among the many scriptures, The Zhouyi cantong qi (周易參同契, Token for Joining the Three in Accordance with the Book of Changes) is the main Chinese alchemical scripture. This book is composed with three kinds of subject, Zhouyi(周易, the Book of Changes), the Huanglao(黃老) Tradition and alchemy(鍊金, 爐火). The author's name is not signed but is concealed in the text. According to the traditional account, the legendary Han immortal from Guiji (會稽, in present-day Zhejiang, 古 浙江), Wei Boyang(魏伯陽), wrote it in the period between Emperor Shun and Emperor Huan of the Eastern Han (126-127 BC), after reading the Longhu jing (龍虎經, Scripture of the Dragon and Tiger). Later he transmitted it to Xu Congshi(徐從事), who appended a commentary, and to Chunyu Shutong(淳于叔通), who first circulated it in the world. While some features of this account provide significant details - especially about the reputed date of the text and about its formation having taken place in stages - the received Cantong qi(參同契) actually is not the product of a single generation of authors, but the result of several centuries of textual accretions as well as theory of three co-authorship by Wei Boyang(魏伯陽), Xu Congshi(徐從事), Chunyu Shutong(淳于叔通). It has over 6000 characters in four-word or five-word verses. Some parts of the book are in styles of prose and poem. Many scholars explain the title "cantongqi(參同契)", saying that "Can(參)" means three, "Tong(同)" means correspondence, and "Qi(契)" means unification. Through images of hexagrams of the Book of Changes, the book illustrates the thought of the Huanglao(黃老) Tradition and alchemy. Wei Boyang(魏伯陽) theorizes his own experience unifying the way of intercourse of Yin and Yang in the Book of Changes, the cultivation of spirit through spontaneity of the Huanglao(黃老) Tradition and the elixir refining of alchemy.