王充
Wang Chong gives three contrasts between "genuine" and "imitation" things: the opaque glass "jade" made by Daoist alchemists with the real thing; the artificially made "pearls" with true pearls; and the "instrument" made by liquefying five different minerals, which can concentrate the sun's rays like the traditional bronze burning-mirror. Furthermore, Needham and Wang question why the "Lunheng" specifies five different minerals,