Prostitutes appear in erotic art in Pompeii and Herculaneum, including wall paintings from buildings identified as brothels, in which they are often nude except for a strapless bra "(strophium)". The paintings illustrate various sexual positions that contradict some scholarly claims about the preferences of Roman men in heterosexual acts. Literary sources record that prostitutes wore distinctive clothing, often gaudy dresses of see-through silk. They were the only Roman women who wore the toga, the distinctive dress of a free Roman male. This crossing of gender boundaries has been interpreted variously.