Zhang heng (78 ~ 139) was a famous scientist and writer in the eastern han dynasty. Zhang heng is diligent and studious, talented and famous. Due to his early death and poor family, he was unable to study for a long time, and returned to his hometown nanyang, where he was invited to serve as the master book, during which he wrote many classics. Zhang heng study very hard, learning is not enough during the day, night still insist on study, study all night, with love of home, created a passionate "nunn fu", eulogized hometown was magnificent, fertile land, rich products.