《旧唐书·列传·卷二十九》
 《易经》说： 古代安葬，用柴草覆盖死者，不筑坟，不立碑，守孝时间长短不论。
《易》曰： 古之葬者，衣之以薪，不封不树，丧期无数。 
The "Book of Changes" says: In ancient burials, the dead were covered with firewood, not built with tombs, no tombstones, and no mourning time.