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
Yang Yin Xiaoming, Northern Wei was suffering greatly from agrarian rebellions, and Yang Jing was commissioned with an army as the governor of Ding Province, roughly modern Baoding, Hebei). Yang Yin accompanied his father to Ding Province, and on account of his contribution to his father's campaign, was created the Baron of Weichang. However, in spring 528, Ding Province fell to the rebel general Du Luozhou, and Yang Jing's household was imprisoned by Du. Soon thereafter, Du was defeated by another rebel general, Ge Rong. Ge wanted to marry one of his daughters to Yang Yin and make him an official, but