Ruth Mazo Karras states that William Peraldus' treatise Summa de virtutibus et vitiis distinguished between sins against nature that were "according to the substance" (intercourse other than vaginal) and "according to the manner, as when a woman mounts."
Ruth Mazo Karras menyatakan bahwa risalah William Peraldus yang berjudul Summa de virtutibus et vitiis membedakan antara dosa melawan alam yang "berdasarkan substansi" (persetubuhan selain vaginal) dan "berdasarkan cara, seperti ketika wanita berada di atas."