[Source] Zhuge Liang's "Memorial on the March Out" (Shu Kingdom, Three Kingdoms period).
[Explanation] "Gu" means to visit; "mao lu" means thatched cottage. It refers to visiting someone at their humble home three times. This idiom metaphorically describes sincere and earnest efforts, repeatedly inviting or visiting a learned and capable person.
[Historical Anecdote] At the end of the Eastern Han Dynasty, eunuchs monopolized power and the imperial government declined, causing heroes from all over the land to raise armies. Liu Bei, a member of the Han royal family, had been raising troops for many years. Many people came to join him, and he himself actively sought out talented individuals. Once, his strategist Xu Shu recommended Zhuge Liang to him. Upon hearing this, Liu Bei was overjoyed and decided to personally visit Zhuge Liang.
Zhuge Liang lost both parents at an early age. After coming of age, he built a few thatched cottages on Wulong Ridge in Longzhong and settled down. He was well-read and highly knowledgeable, with deep insights into the affairs of the realm. He often compared himself to Guan Zhong and Yue Yi, famous statesmen and generals from the Spring and Autumn and Warring States periods. Those who knew him well considered him extraordinary and respectfully called him "Master Wulong" (the Sleeping Dragon).
Liu Bei, accompanied by Guan Yu and Zhang Fei and carrying gifts, traveled through the night to Longzhong. The young servant at the gate, upon learning they had come to see his master, replied, "The master is not at home. He left early this morning; I don't know where he went, nor when he will return." Liu Bei had no choice but to leave Wulong Ridge in disappointment.
A few days later, Liu Bei learned that Zhuge Liang had returned home. Again accompanied by Guan Yu and Zhang Fei, he braved a heavy snowfall to travel to Longzhong. However, upon arrival, he learned that Zhuge Liang had left the day before with a friend for a journey of leisure, and the three men once again came up empty-handed.
Some time later, Liu Bei prepared for a third visit to invite Zhuge Liang. Guan Yu and Zhang Fei were somewhat annoyed, but Liu Bei remained undeterred. The three men arrived once more at Wulong Ridge. Hearing from the young servant that Zhuge Liang was sleeping, Liu Bei respectfully stood waiting on the steps of the thatched hall. After a long while, the servant finally came out and invited the three men into the cottage, announcing that the master had awakened.
After they were seated, Liu Bei and Zhuge Liang introduced themselves and began discussing the affairs of the realm. Liu Bei expressed his determination and desire to bring a better life to the common people. Seeing Liu Bei's humility and sincerity, Zhuge Liang said, "Jing Province has a strategic location, an excellent place for military operations. Since Liu Biao cannot hold it, you, General, should take it for yourself. First, secure Jing Province and establish a solid base. Then, take Yizhou. After that, form an alliance with Sun Quan and foster good relations with the various tribes in the southwest. When the time is right, advance toward the Central Plains. In this way, the great enterprise of unifying the empire can be achieved."
After hearing this, Liu Bei was profoundly impressed and utterly convinced. He then expressed his wish for Zhuge Liang to come out of seclusion and assist him. Zhuge Liang did not decline. The very next day, he left with Liu Bei for Xinye. From then on, Zhuge Liang used all his wisdom and talent to assist Liu Bei in his quest to conquer the empire.