《旧唐书·列传·卷一百三十八》
据封禅祭祀天地的礼仪来看，天亮前三四个小时，宰人用有铃的鸾刀斩杀牲畜，待天亮时进行祭祀。
据封禅祀礼曰：未明十五刻，宰人以鸾刀割牲，质明而行事。
According to the etiquette of the sealing ceremony to worship heaven and earth, three or four hours before daybreak, the slaughterer used the bell-shaped Luan knife to kill the sacrificial animals, and the sacrifice was performed at daybreak.