《旧五代史·后周·太祖纪四》
到下葬陵墓时，召附近三十家交纳国税的人家作为守陵的民户，下葬前揭开瓦棺盖，先检查墓穴内，千万不要伤了别人性命。
临入陵之时，召近税户三十家为陵户，下事前揭开瓦棺，遍视过陵内，切不得伤他人命。
When burying the tomb, summon 30 nearby households who have paid national taxes to be the tomb guardians. Before burying, remove the lid of the terracotta coffin and first inspect the tomb. By no means should anyone else's life be put at risk.