Chinese alchemy

By western standards, the Taoist texts are fairly explicit; Jean Cooper writes in Chinese Alchemy: The Taoist Quest for Immortality:

Herbal medicines and drugs play a more important part in Chinese alchemy than in the western branches. Plant-produced drugs were supposed to give quick but more transient results, while those from minerals were slower but surer . . . although authorities like Ko Hung assert that metals produce better results in this world, it must be remembered that the immortals of the Isle of P’eng used herbs, since the herbs of immortality grew there and it was to obtain these that the various expeditions were mounted.[1]

In the classic Science and Civilization in China, Joseph Needham and Gwei-Djen Lu conjectured:

there is much reason for thinking that the ancient Taoists experimented systematically with hallucinogenic smokes, using techniques which arose directly out of liturgical observance . . . the incense-burner remained the centre of changes and transformations associated with worship, sacrifice, ascending perfume of sweet savour, fire, combustion, disintegration, transformation, vision, communication with spiritual beings, and assurances of immortality. Wai tan and nei tan met around the incense-burner. Might one not indeed think of it as their point of origin?[2]

[1] Cooper, Jean. Chinese Alchemy: The Taoist Quest for Immortality. New York: Sterling, 1990

[2] Science and Civilization in China: Vol. 5, 1974 p. 154 Gwei-Djen Lu Science and Civilisation in China: Volume 5, Chemistry and Chemical Technology, Part 2, Spagyrical Discovery and Invention: Magisteries of Gold and Immortality