《汉书·志·郊祀志下》
《易》有八卦，《干》《坤》六子中，水火不相及，雷风不相悖，山河气息相通，这样才能进行变化，全面形成万物。
《易》有八卦， 乾 、 坤 六子，水火不相逮，雷风不相誖，山泽通气，然后能变化，既成万物也。
The Book of Changes has eight trigrams, and among the six sons of "Qian" and "Kun," water and fire do not reach each other, thunder and wind do not contradict each other, mountain and river breathe together, so that they can change and evolve to form all things.