《周礼·春官宗伯·大卜&诅祝》
凡卜筮，君观察兆象，大夫观察兆气，史官观察兆的粗纹，卜人观察兆的细纹。
凡卜筮，君占体，大夫占色，史占墨，卜人占坼。
In all divination and divination, the monarch observes the signs, the doctor observes the aura, the official historian observes the coarse lines of the signs, and the diviner observes the fine lines of the signs.