《墨子·52章 备城门》
城墙的四边和四角都建高高的望敌楼，使贵家子在楼上了望敌人，观察敌人的势态，进及左右移动的地方。失职者处以斩刑。
孔之，各为二慕二，一凿而系绳，长四尺。城四面四隅皆为高磨■，使重室子居其上候适，视其态状与其进左右所移处，失候斩。
High watchtowers were built on all four sides and corners of the city wall, so that the noblemen could look out over the enemies, observe their movements, and advance and retreat in time. Those who failed to do so were executed.