Chinese sun and moon mirrors being hung round the neck, or because necks are concave things. Liu An's (c. 139 BCE) "Huainanzi" "Masters of Huainan", which is a compendium of writings from various schools of Chinese philosophy, was the first text to record "fangzhu" dew-collectors. Two "Huainanzi" chapters metaphorically use "sun and moon mirrors" to exemplify "yang" and "yin" categories and elucidate the Chinese notion of "ganying" "cosmic resonance" through which categorically identical things mutually resonate and influence each other. The "yángsuì" 陽燧 "burning-mirror" is "yang", round, and sun-like; the "fāngzhū" 方諸 "square receptacle" is "yin", square, and moon-like. The first context describes "yangsui" and
Zhou Dunyi credited in Taoism as the first philosopher to popularize the concept of the taijitu or "yin-yang symbol". Born in 1017 in Yingdao County, Daozhou prefecture, in present-day Yongzhou, southern Hunan, Zhou was originally named Zhou Dunshi. Raised by a scholar-official family, he was changed his name in 1063 to avoid a character in the personal name of the new Emperor Yingzong. His father died when he was fourteen and he was taken in by his uncle Zheng Xiang. He received his first posting in government through his uncle. Although very active in his civil service career, he never did achieve