Natural History (Wolves; The Origin of the Story of Versipellis)
Pliny the Elder, Natural History, 8.34 from The Perseus Digital Library.
Euanthes, a Grecian author of no mean reputation, informs us that the Arcadians assert that a member of the family of one Anthus is chosen by lot, and then taken to a certain lake in that district, where, after suspending his clothes on an oak, he swims across the water and goes away into the desert, where he is changed into a wolf and associates with other animals of the same species for a space of nine years. If he has kept himself from beholding a man during the whole of that time, he returns to the same lake, and, after swimming across it, resumes his original form, only with the addition of nine years in age to his former appearance. To this Fabius adds, that he takes his former clothes as well. It is really wonderful to what a length the credulity of the Greeks will go! There is no falsehood, if ever so barefaced, to which some of them cannot be found to bear testimony.
So too, Agriopas, who wrote the Olympionics, informs us that Demænetus, the Parrhasian, during a sacrifice of human victims, which the Arcadians were offering up to the Lycæan Jupiter, tasted the entrails of a boy who had been slaughtered; upon which he was turned into a wolf, but, ten years afterwards, was restored to his original shape and his calling of an athlete, and returned victorious in the pugilistic contests at the Olympic games.
Euanthes, inter auctores Graeciae non spretus, scribit Arcadas tradere ex gente Anthi cuiusdam sorte familiae lectum ad stagnum quoddam regionis eius duci vestituque in quercu suspenso tranare atque abire in deserta transfigurarique in lupum et cum ceteris eiusdem generis congregari per annos VIIII. quo in tempore si homine se abstinuerit, reverti ad idem stagnum et, cum tranaverit, effigiem recipere, ad pristinum habitum addito novem annorum senio. id quoque adicit, eandem recipere vestem.
mirum est quo procedat Graeca credulitas! nullum tam inpudens mendacium est, ut teste careat. item Agriopas, qui Olympionicas scripsit, narrat Demaenetum Parrhasium in sacrificio, quod Arcades Iovi Lycaeo humana etiamtum hostia facebant, immolati pueri exta degustasse et in lupum se convertisse, eundem X anno restitutum athleticae se exercuisse in pugilatu victoremque Olympia reversum.