Keats based his poem on the folk belief that a girl could see her future husband in a dream if she performed certain rites on the eve of St. Agnes; that is she would go to bed without any supper, undress herself so that she was completely naked and lie on her bed with her hands under the pillow and looking up to the heavens and not to look behind. Then the proposed husband would appear in her dream, kiss her, and feast with her.