《汉书·传·赵尹韩张两王传》
心思的细微之处口中无法说清，言语的微细之处笔下无法讲明，因此伊尹五次被推荐给桀，五次奉事汤，萧相国推荐淮阴侯几年才得以任用，况且臣在千里之外，凭藉文书禀告事情呢！
夫心之精微口不能言也，言之微眇书不能文也，故伊尹五就桀，五就汤，萧相国荐淮阴累岁乃得通，况乎千里之外，因书文谕事指哉！
The subtleties of thought cannot be explained in words, and the nuances of speech cannot be expressed in writing. This is why Yi Yin was recommended to King Jie five times and served Tang five times, and Prime Minister Xiao recommended the Marquis of Huaiyin for several years before he was employed. How can I, a subject, inform you about events from a thousand leagues away by submitting written reports?