There is a legend in it: a long time ago (I can't remember the Qing Dynasty, hehe), several juren who had taken the exam got together to chat. One of them counted the places of interest in his hometown and then asked others questions arrogantly. Shandong juren said airily that "one mountain, one water and one saint" and compared them.
One Mountain: the only Mount Tai among the Five Mountains.
One water: the Yellow River, with water in one garment; Mother river.
A saint: Kong Old Master Q Q.