Woodcut illustrating the principle that the face is 'Yang within Yang' and can therefore resist cold. From 'Problem 36', Tu zhu ba shi yi nan jing bianzhen (Corrected Edition of the Canon of Problems, Illustrated and Annotated), published in the Wan Li reign period of the Ming Dynasty (1573-1620).
The head is the part of the body where all the Yang channels converge; the Yin channels all ascend to the neck or the middle of the thorax, but only the Yang channels extend as far as the head and the ears. Thus the face is 'Yang within Yang', and can consequently withstand cold influences.
