Megillos is a fictional character created by Lucian, a second century Assyrian rhetorician, as part of his Dialogues of the Courtesans series. One sex worker tells another of a pair of clients she’d had who she assumed were both women. However, over the course of the transaction, one had removed a wig, and insisted that he was a man despite having “a body entirely like that of all women”; when the courtesan argued with him, he rebuked her, saying, “Don’t you effeminate me!” The two of them, along with the remaining woman (Demonassa, Megillos’ wife), then had sex, which the courtesan, ashamed of the encounter, refuses to speak to her colleague about in any detail.
Though commonly described as a lesbian story (including here, where the full translated text is stored), Megillos’ self-expressed identity as a man means that the story better fits a transgender mold. For a longer scholarly takedown of the linguistic evidence, see here.