In the Graeco-Roman world, practitioners of magic were known as magi (singular magus), a "foreign" title of Persian priests. Apuleius, defending himself against accusations of casting magic spells, defined the magician as "in popular tradition (more vulgari)... someone who, because of his community of speech with the immortal gods, has an incredible power of spells (vi cantaminum) for everything he wishes to." Pliny the Elder offers a thoroughly skeptical "History of magical arts" from their supposed Persian origins to Nero's vast and futile expenditure on research into magical practices in an attempt to control the gods. Philostratus takes pains to point out that the celebrated Apollonius of Tyana was definitely not a magus, "despite his special knowledge of the future, his miraculous cures, and his ability to vanish into thin air".