《论衡·卷十六·乱龙篇》
玳瑁壳经摩擦能吸引细小的东西，磁石能够吸引铁针，都因为它们是真实的东西，不能借用别的相类似的东西。
顿牟掇芥，磁石引针，皆以其真是，不假他类。
When tortoiseshell is rubbed, it can attract small objects; magnets can attract iron needles; these are because they are real objects and cannot borrow from other similar objects.