《论衡·卷二十四·讥日篇》
洗头是洗去头上的污垢，帽子是头上的装饰品；洗澡是洗去身上的垢泥，衣服是防护身体受寒。
且夫沐去头垢，冠为首饰；浴除身垢，衣卫体寒。
Washing hair is to wash away dirt on the head, a hat is an ornament on the head; bathing is to wash away dirt on the body, clothes are meant to protect the body from the cold.