《搜神记·卷三》
段留给他配了些膏药，并用竹简写了封信一起封在竹筒里，告诉这学生说： 碰上急事，就打开这竹筒看看。 
医为合膏药，幷以简书封于筒中，告生曰： 有急，发视之。 
Duan Yu gave him some ointment and wrote a letter on bamboo slips, which he sealed inside a bamboo tube, telling the student, "If something urgent happens, open the tube and consult it. "