《旧唐书·列传·卷一百一十六》
以至于口舌生疮，手肘生茧，人到壮年肌肤也不丰满，未至老年却已脱了牙齿白了头发，眼花缭乱好像无数飞蝇垂珠在眼睛里乱动，这都是刻苦努力学习造成的。
以至于口舌成疮，手肘成胝。既壮而肤革不丰盈，未老而齿发早衰白；瞀然如飞蝇垂珠在眸子中者，动以万数，盖以苦学力文之所致！
So much so that my tongue was sore and my elbows were calloused. When I was in my prime, my skin was not full, and before I was old, my teeth had fallen out and my hair had turned white. My eyes were blurred, as if countless flies were flying around in my eyes, which were all caused by my hard work.