In the ancient Tang Dynasty, there was a student who was on his way to the capital to attend the national examination, from which the top students would be selected as ministers in the Imperial court.

Unfortunately, he fell ill halfway when passing through a mountain village. Thanks to an herbalist doctor and his daughter, he was taken to their house and treated well. He recovered quickly, due to the father and daughter's good care. Well, when he had to leave, he found it hard to say goodbye to the pretty girl; so did she. They fell in love. So the girl wrote down the right-hand part of an antithetical couplet for the student to match: "Green trees against the sky in the spring rain while the sky set off the spring trees in the obscuration."

"Well, I can match it, though it is not easy. You'll have to wait until I have finished the examination," replied the student. The young girl nodded in agreement.

At the examination, the young man won first place and was congratulated by the emperor. The winners were then interviewed and tested by the emperor. As luck would have it, he was asked by the emperor to finish a couplet. The emperor wrote: "Red flowers dot the land in the breeze's chase while the land colored up in red after the kiss." The young man realized immediately that the girl's couplet was the perfect fit to the emperor's couplet, so he took it for his answer without hesitation.

The emperor was delighted to see the matching half of his couplet. It was so harmonious that he authorized the young man's appointment as a minister in his court and allowed him to pay a visit to his hometown before taking up the post. The young man happily returned to the girl's home and told her the emperor's couplet. They were soon married. For the wedding, the couple doubled the Chinese character for "happy" on a red piece of paper and afixed it to a wall to express their happiness for the two events. Since then, it has become an important social custom at weddings.