The first of the plots, the winning-the-bride tale, is very much like an old folktale or fairytale. In the source story, a suitor named Giannetto attempts to win a beautiful woman as his bride by passing a test. The test simply involves staying awake all night. However, on his first two attempts he fails the test because he is given a sleeping potion. But on the third attempt a sympathetic maid warns him not to drink the drugged wine, and so Giannetto wins thebride.
Shakespeare went beyond this earliest source and made the winning of the bride more complicatedbyinvolving a choice of three caskets or boxes, one of which contains a portrait of the lady. The suitor must choose the correctcasket based on various clues; but, if he fails to choose correctly, he must give up all hope of marriage to anyone. There are several possible sources that Shakespeare may have used for the use of caskets (instead of the sleep test), and Shakespeare could possibly have used more than one of these sources when he created his play. The change, however, was definitely an improvement over Fiorentino’s version because Shakespeare was thus able to integrate the two parts of his play more completely by intertwining thematic aspects of the plots. Shakespeare’s play thus has greater overall unity andintegrity.