Cantong qi

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The Cantong qi is deemed to be the earliest book on alchemy in China. The title has been variously translated as Kinship of the Three, Akinness of the Three, Triplex Unity, The Seal of the Unity of the Three, and in several other ways. The full title of the text is Zhouyi cantong qi, which can be translated as, for example, The Kinship of the Three, in Accordance with the Book of Changes.

According to the well-established view in China, the text was composed by Wei Boyang in the mid-second century CE, and deals entirely with alchemy, in particular with Neidan (or Internal Alchemy). In agreement with its title, the Cantong qi is concerned with three major subjects, Cosmology (the system of the Book of Changes), Taoism (the way of "non-doing"), and Alchemy.