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
Taijitu the 16th century. The original description of a "taijitu" is due to Song era philosopher Zhou Dunyi (1017–1073), author of the "Taijitu shuo" "Explanation of the Diagram of the Supreme Ultimate", which became the cornerstone of Neo-Confucianist cosmology. His brief text synthesized aspects of Chinese Buddhism and Taoism with metaphysical discussions in the "Yijing". Zhou's key terms Wuji and Taiji appear in the opening line , which Adler notes could also be translated "The Supreme Polarity that is Non-Polar". Non-polar ("wuji") and yet Supreme Polarity ("taiji")! The Supreme Polarity in activity generates "yang"; yet at the limit of activity it