Explanation: As stable as Mount Tai. Used to describe something extremely firm and immovable.
This idiom originates from "A Memorial Advising King Wu" by Mei Cheng during the Western Han Dynasty: "If you can listen to the words of loyal ministers, every endeavor will surely bring joy. If you persist in doing as you desire, your danger will be greater than a pile of eggs, and your task harder than ascending to heaven. But if you change your intentions, it will be easier than turning over your palm, and your position will be as secure as Mount Tai."
Mei Cheng, styled Shu, was a famous literary figure of the Han Dynasty, from Huaiyin in the Western Han (present-day Jiangsu province). During the reign of Emperor Jing of Han, he served as Langzhong (a court official) in the court of Liu Bi, King of Wu.
Wu was a major feudal state among the vassal kingdoms at the time. Liu Bi harbored great ambitions, resented the central government, and secretly plotted rebellion. Emperor Jing appointed the capable politician Chao Cuo as Imperial Censor. Chao Cuo advocated reducing the territories of the feudal princes to strengthen the central government's power and prestige and consolidate national unity. Seeing that several other princes had already had their lands reduced, Liu Bi knew he would not be spared. Thus, he contacted the kings of Chu, Zhao, Jiaoxi, and Jiaodong to conspire and plan a rebellion.
Clearly recognizing the dangers of Liu Bi's planned rebellion, Mei Cheng wrote "A Memorial Advising King Wu" to dissuade him. In his memorial, he said: "If Your Majesty can heed the advice of loyal ministers, all disasters can be avoided. If you insist on following your own desires, your peril will be greater than a stack of eggs, and your task harder than ascending to heaven. However, if you can quickly change your original intentions, it will be easier than turning over your palm, and your position will be as stable as Mount Tai."
But Liu Bi remained obstinate and intensified his secret activities. Thus, Mei Cheng had no choice but to leave the state of Wu and became a guest in the court of Liu Wu, Prince Xiao of Liang. In 154 BC, Liu Bi contacted the kings of Chu, Zhao, Jiaoxi, and Jiaodong, launching a rebellion under the banner of "removing the evil ministers surrounding the emperor" and "killing Chao Cuo." This event is known in history as the "Rebellion of the Seven States (Wu and Chu among them)."
Emperor Jing, believing slanderous accusations, executed Chao Cuo to appease the feudal kings. At this point, Mei Cheng wrote another memorial, "A Second Memorial Advising King Wu," urging Liu Bi to cease hostilities. But Liu Bi still refused to repent. Soon, the Han general Zhou Yafu led imperial forces to defeat the rebel armies of Wu and Chu. The King of Chu, Liu Wu, committed suicide; Liu Bi fled to Dong'ou but was killed there; the other five rebel kings also ended up either committing suicide or being executed. This rebellion was completely crushed within just three months. After the Rebellion of the Seven States was quelled, Mei Cheng gained widespread fame for his foresight and wisdom demonstrated in "A Memorial Advising King Wu."
Later, when Emperor Wu of Han ascended the throne, he sent people to summon Mei Cheng to serve in the capital. Sadly, Mei Cheng died on his journey before reaching the capital.