This is from the New Tang Dynasty Book - Li Mi Biography: "I heard that Bao Kai was in Monkey Mountain, and I went to follow him. He took a cow with a bushel blanket and hung a book of Han Shu on the corner, traveling and reading."

Li Mi, a native of Xiangyang in the Sui Dynasty, was dedicated to learning and never wasted time, so his study life was quite intense. Once, he went to Sui Mountain (there is a monkey mountain), he was afraid of too much delay during the journey, so before he set off, he came up with a good way to read while traveling: he placed a thin ball on the back of an ox, and hung the "Book of Han" he wanted to read on the horn of the ox. In this way, he could ride the animal comfortably, holding the book in one hand and the reins in the other, and walking, even no different from reading in the house.

Walking on the way, because Li Mi was so concentrated, he was so motionless that he actually looked like a statue posing on the back of an ox. Coincidentally, the court minister Yang Su passed by here, see the bull on the back and this kind of good learning, they do not care about their own rush, quietly follow the back, walked a large section of the road, Li Mi did not know. Until he moved the head of the cow, intending to change another book, Yang Su only and he struck up a conversation, asked him to read what book? At this time, Li Mi also just barely moved his head, glanced to his side, and said lightly, "Read the biography of Xiang Yu!"