Ouyang Hsiu was one of the Eight Masters of Literature of the T'ang and Sung dynasties (618--1279). His father died when he was four and his upbringing was due entirely to his mother's hard work and diligence. She did not want him to miss out on an education just because they were poor, so she decided to be his teacher herself.
But, she thought, "We're poor and can't afford writing materials. I'll have to think of some way other way." Just then she saw some birdtracks left on the shore. "That's it!" she thought. "Why don't I write on the sand and teach little Ah Hsiu that way?" ("An Hsiu" was the boy's nickname.)
She called her son over to help her dig a hole and spread out some sand. Then she used a reed to write the character for "sky." When the boy had learned that, she smoothed out the sand and taught him "person." Ah Hsiu used the sandbox every day for practice. He later became a successful, accomplished writer.
Ouyang Hsiu's mother has served as a model to later generations, and "drawing characters with a reed to teach the child" has become a proverbial expression for a patient, caring mother.