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
Yin and yang with fire, sky, the sun, masculinity and daytime. The yin-yang symbol, having no "officially standardized" rendition, has been the basis of much artistic variation, most of it "frivolous" (that is, "merely" artistic, with no philosophical/mystical meaning, e.g., tattoos). Yin and yang also applies to the human body. In traditional Chinese medicine good health is directly related to the balance between yin and yang qualities within oneself. If yin and yang become unbalanced, one of the qualities is considered deficient or has vacuity. In the "I Ching", originally a divination manual of the Western Zhou period (c. 1000–750 BC), yin and