According to Chinese mythology, the god in charge of the Yellow River was named He Bo. One year, as the autumn was coming, torrential rain had been falling for days on end, and the hundred streams were all discharging themselves into the Yellow River, which made it even broader.
One, standing on one side of the river, could not distinguish an ox from a horse on the opposite bank. Thus He Bo was even more proud, thinking that all the magnificent sights were accumulated here.
Then looking across the expanse, He Bo turned his face to the God of North Sea and said with a sigh, " As the vulgar saying goes, some people go so far as to think that they are more knowledgeable than anybody else when they have got some knowledge. Now I know it was surely spoken of me. And moreover, I have heard that some made little of the knowledge of Confucius and the righteousness of Bo Yi (A loyal minister of Shang Dynasty, when Shang was conquered by Zhou Dynasty, Bo Yi considered it unrighteous to eat the grain of Chou and thus fled and hid on Shou Yang Mountain, where he tried to live by gathering ferns to eat.), and at first I did not believe them. Now I behold the all-but-boundless extent of your realms. If I had not come to your gate, I should have been in danger of continuing in my ignorance, and been laughed at for long by sensible people."
This Chinese fable story is from "The Floods of Autumn" (秋水), an article of Zhuang Zi.
The Chinese idiom produced by this Chinese fable story was "Wang Yang Xing Tan", which originally meant feeling one's own littleness upon seeing another's might. Now it is mostly used to indicate being able to do nothing but sigh in the face of a huge task.
Like other stories in Zhuang Zi's articles, this one is intended to tell some point of Taoists' theory, that is, there is always someone better. Besides, Zhuang Zi used this story to criticize Confucius for showing off his knowledge just like He Bo proud of his greatness.