《明史·志·卷三十七》
至于六变而天神下降，八变而地神至，九变而人鬼享祀，并不是有难易的分别。
至若六变而天神降，八变而地祇格，九变而人鬼享，非有难易之分。
As to the six changes that cause the gods of Heaven to descend, the eight changes that cause the gods of Earth to arrive, and the nine changes that cause humans and ghosts to enjoy sacrifices, there is no distinction between difficulty and ease.