《天工开物·下篇·五金》
宋先生说：人分十个等级，从高贵的王、公到低贱的舆、台，其中缺少一个等级，人的立身处世之道就建立不起来了。
宋子曰：人有十等，自王公至于舆台，缺一焉而人纪不立矣。
Mr Song said: There are ten levels of people, from noble kings and dukes to lowly laborers and entertainers. If one of these levels is missing, the way for people to establish themselves in the world cannot be established.