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
Dualistic cosmology able to transmute into each other. In the yin-yang symbol there is a dot of yin in yang and a dot of yang in yin. In Taoism, this symbolizes the inter-connectedness of the opposite forces as different aspects of Tao, the First Principle. Contrast is needed to create a distinguishable reality, without which we would experience nothingness. Therefore, the independent principles of yin and yang are actually dependent on one another for each other's distinguishable existence. The complementary dualistic concept seen in yin and yang represent the reciprocal interaction throughout nature, related to a feedback loop, where opposing forces do