Erotic art, especially as preserved in Pompeii and Herculaneum, is a rich if not unambiguous source; some images contradict sexual preferences stressed in literary sources and may be intended to provoke laughter or challenge conventional attitudes. Everyday objects such as mirrors and serving vessels might be decorated with erotic scenes; on Arretine ware, these range from "elegant amorous dalliance" to explicit views of the penis entering the vagina. Erotic paintings were found in the most respectable houses of the Roman nobility, as Ovid notes: