《后汉书·列传·荀韩钟陈列传》
孔子说 ：以前圣人作《易》，高则向天观象，下则于地察法，看鸟兽的文采，与地之所宜。
孔子曰 昔圣人之作《易》也，仰则观象于天，俯则察法于地，睹鸟兽之文，与地之宜。
Confucius said: In the past, the holy sages wrote the "Book of Changes" and looked up at the sky to observe the phenomena and down to the earth to observe the laws, looking at the colors of birds and animals and the nature of the earth.