Li Mi served as a palace guard for Emperor Yang of the Sui Dynasty. One day at court, the emperor asked General Yuwen Shu, "Who is that dark-faced young man standing in the left guard formation?" "That is Li Mi, son of the former minister Li Kuan," Yuwen Shu replied. The emperor observed, "That man keeps glancing around—he is no ordinary person and should not remain a guard." A few days later, Yuwen Shu told Li Mi, "Your family has served as officials for generations. You should seek advancement through scholarship, not through guard duty."
Li Mi then feigned illness to resign from his post and devoted himself to intense study. One day, while riding an ox to Mount Goushi, he hung a copy of the *Book of Han* from the ox's horn and read as he traveled. The Duke of Yue, Yang Su, happened upon him and asked, "What book is so important that you read while riding?" Li Mi replied, "The *Book of Han*—I cannot bear to waste a moment." Impressed by his dedication, Yang Su praised him as a man of exceptional talent.
"Which scholar is this diligent?" Yang Su asked.
Li Mi, recognizing the Duke of Yue, quickly bowed in respect.
After speaking with Li Mi, Yang Su found him to be an extraordinary talent and told his son Yang Xuangan, "Li Mi is no ordinary man." Yang Xuangan then became close friends with Li Mi. One day, he asked, "The Sui Dynasty won't last much longer. If chaos erupts, which of us can seize control?" Li Mi replied, "In leading troops into battle, I am not as bold as you. But I can command the heroes of the world to follow my orders."
Yang Xuangan was later ordered to guard Liyang and oversee grain transport, where he welcomed Li Mi. Inspired and strategized by Li Mi, Yang Xuangan raised an army against the Sui Dynasty but was soon defeated and killed. Li Mi was captured but escaped en route, fleeing to join the Wagang rebel army.
After joining the Wagang rebels, Li Mi earned the trust of their leader Zhai Rang and was elevated to command, proclaiming himself Duke of Wei with the reign title Yongping. He appointed many surrendered Sui officials and generals, then had Zhai Rang killed. Later, Li Mi submitted to Yang Tong, the Sui Prince of Yue who had declared himself emperor in Luoyang, but after losing a battle against the Tang general Wang Shichong, he surrendered to the Tang dynasty and was soon executed for plotting rebellion.
Later, the idiom "Hanging Books on Ox Horns" came to be used as a metaphor for diligent study.
Source: *New Book of Tang*, "Biography of Li Mi"
Meaning of the Idiom: Later, the Chinese idiom "牛角挂书" came to describe a metaphor for diligent study.