Yin and Yang
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Yin (black) and Yang (white). The two inner dots represent Yin within Yang and Yang within Yin. Around the circumference are shown the ☞ eight trigrams (bagua), which here represent different stages in the cycles of increase and decrease of Yin and Yang (clockwise from the lower left corner: zhen, li, dui, qian, sun, kan, gen, and kun).
Source: Hu Wei (1633-1714), Yitu mingbian
(Clarifications on Charts Related to the Book of Changes; 1706), chapter 3.