《宋书·志·卷十八》
《晋令》规定： 乘驿车出使，遇有丧事，便自己上表章奏报朝廷，允许穿白色丧服乘骡车，到达后由副使代理其事。 
《晋令》曰： 乘传出使，遭丧以上，即自表闻，听得白服乘骡车，到副使摄事。 
According to the Regulation of the Jin Dynasty: When going on a mission in a postal carriage, if a funeral is encountered, a request will be submitted to the court and permission will be granted to wear white funeral clothes and ride a mule cart. After arriving at the destination, the deputy envoy will take over.