《史记·三十世家·外戚世家》
魏媪到许负那里去看相，让他给薄姬相面，许负说她一定能够生下天子。
媪之许负所相，相薄姬，云当生天子。
Wei Ao visited Xu Fu to have his fortune told, and asked him to tell the fortune of his niece Bo Ji, and Xu Fu said that she would give birth to an emperor.