《孟子·梁惠王章句上·第八节》
 称一称才知道物体的轻重，量一量才知道物体的长短，所有事物都是如此，人心更是这样。
 权，然后知轻重；度，然后知长短。物皆然，心为甚。
Weighing it will tell you the weight of an object, and measuring it will tell you the length of an object. This is true for all things, and it is even more true for the human heart.