《周礼·夏官司马·候人&司右》
所设的漏壶都设有专人用水火在一旁守候，并负责区分昼漏和夜漏的长短。
凡丧，县壶以代哭者，皆以水火守之，分以日夜。
A water clock was set up and a person was specially assigned to look after the fire and water next to it, who was then responsible for keeping track of the difference between the length of the day and night.