This legend is about Li Bai, a great poet in Tang Dynasty.
Li Bai was naughty and disliked study when he was a child. One day he saw an old woman grinding an iron rod on a big stone when he was playing by a river. Driven by curiosity, Li Bai came up and asked,
"What are you doing, granny?"
"Grinding an iron rod," said the old women without stopping grinding.
"Then what for?" he asked again.
"To make a sewing needle," was the answer.
"What?!" little Li Bai was puzzled, "you want to grind so big a rod into a needle? It will take many years."
"This doesn't matter. As long as I persevere in doing so, there is nothing you cannot achieve in the world. Certainly I can make a needle from the rod."
Deeply moved by what the old woman said, Li Bai took effort to study since then and finally became one of the greatest poets in China.
So long as you have put a great deal of effort, you can grind an iron rod into a needle-Perseverance spells success