In Chinese dichotomy, the sun is yang (positive, active, or male) and the moon is yin (negative, passive, or female). According to the book Chou Li, the Chou emperors (1122-249 B.C.) had the custom of praying to the moon on the 15th night of the eighth lunar month. In the Ching dynasty, there were a sun altar in eastern Peking and a moon altar in western Peking; at the time of every autumnal equinox, the emperor offered sacrifices and prayed to the moon at the moon altar.