《明史·志·卷三十三》
在此之前一天，皇帝穿平常服饰在内殿祭告，行四拜礼，如同到郊宫仪式。
前期一日，皇帝常服告于内殿，行四拜礼，如出郊仪。
The day before this, the emperor dressed in ordinary robes and inside the palace, demonstrated worshipping and prostrating himself four times, just like playing the imperial palace ceremony.