In the Yuan play The Chalk Circle, a wife poisons her husband and claims his concubine's son to take the fortune, and Judge Bao tests the two mothers

The Chalk Circle is a fictional zaju play from the Yuan dynasty, attributed to Li Xingdao (also given as Li Qianfu). Zhang Haitang is sold into prostitution after her father dies. The rich and childless Ma takes her as his second wife, and she bears his son and heir. Ma's first wife and her lover, the clerk Zhao, poison Ma and blame Haitang. The first wife then claims the boy is her own child, so the heir and the property are hers. At the first trial the neighbours and midwives, paid by the first wife, give false evidence, and the clerk has Haitang tortured until she confesses. The judge, Su Shun, is a corrupt official who says he knows no law and only wants silver. Haitang is sent to Kaifeng to be executed. There Bao Zheng retries the case. He draws a chalk circle, places the child inside, and tells the two women to pull. Haitang will not pull for fear of hurting him, and Bao rules she is the mother. The poisoners and false witnesses are punished, and Su Shun is dismissed for life. Stanislas Julien's French translation appeared in London in 1832. Bertolt Brecht reworked the story as The Caucasian Chalk Circle in 1944, giving the child to the foster mother who would not pull.