When Liu Zai was the Magistrate of Taixing District, the loss of a golden hairpin was reported to him. Only two women working as servants were present at the scene. Upon being cross-examined neither admitted to stealing the hairpin. Liu Zai ordered them each to take a reed home.
"The reed of the innocent one will remain at the same," said Liu, "but the reed of the guilty one will grow tow inches by tomorrow."
When the reeds were inspected the next day, one was still the same while the other was two inches shorter. The culprit had been afraid that her reed would grow longer. She confessed to the crime.