Great question. I've always wanted to know the story, but I never looked for it. I did a Google search for "move the mountain" AND Chinese and many sites came up.

It comes from 'Yu Gong Yi Shan, literally meaning "foolish man moving the mountain"' cited from the website http://www.caiguoqiang.com/text_writing.php.

I found the text on another site:

A long time ago, there was an old man with his children living in a mountain village. They lived a very happy life, with only one big problem. They had to climb over a big mountain to go to the field everyday. So one day the old man decided to move the mountain. With his children, they began chipping away pieces of rock every day at the foot of the mountain. A wise man passed by and said, 'How can you possibly think you can move the mountain?' The old man said, 'Probably I won't. But you see, I have children. My children will have children. And they will continue and the mountain will be moved.

I hope this helps! It helped me...I've always wanted to know the text.

Big thanks! When English is not your mother tongue, some parts are hard to guess...