Cun, guan, chi pulses, 15th century Chinese woodcut

Illustration of 'Problem 18' in Huang Di ba shi yi nan jing (Canon of Eighty-One [Medical] Problems [in the Inner Canon] of the Yellow Lord), preserved in Zhengtong daozang (Daoist Canon compiled during the Zhengtong reign period [1436-1449] of the Ming Dynasty). 'Problem 18' is explained thus: The male faces south; he turns his back on yang and faces towards yin, like the heavens above. The three yang channels (Greater Yang, Lesser Yang and Reverting Yang) issue from the earth; therefore the chi (proximal radial pulse) is described as 'floating' in the male. The female faces north; she turns her back on yin and faces towards yang, like the earth beneath. The three yin channels (Greater Yin, Lesser Yin and Reverting Yin) issue from the heavens; therefore the chi is described as 'floating' in the female.

In the fifth month the gou trigram appears; in the sixth month the dun trigram appears; in the seventh month the fou trigram appears; tai yin shao yin jue yin (Greater Yin, Lesser Yin, Reverting Yin); in the eleventh month the hou trigram appears; in the twelfth month the lin trigram appears; tai yang shao yang jue yang (Greater Yang, Lesser Yang, Reverting Yang).