No Roman priesthood is as extensively documented in its restrictions as the Flamen Dialis, priest of Jupiter, whose daily life was governed by an unusually long list of prohibitions recorded chiefly by the second-century writer Aulus Gellius in the Noctes Atticae and, from a Greek perspective, by Plutarch in his Roman Questions. The Flamen Dialis could not touch or even name a goat, a dog, raw meat, ivy, or beans; could not touch or be in the presence of iron except a ritual knife; could not ride a horse or even touch one; could not see an army under arms, take an oath, or wear a knotted garment or ring; could not spend a single night away from his own bed in Rome; and if his wife, the flaminica, who held a parallel and equally restricted ritual role, died, he was required to resign the priesthood entirely, since the office and the marriage were treated as a single ritual unit rather than as separable.
Historians of Roman religion read this extraordinary catalogue of taboos in different ways: some treat the Flamen Dialis as a kind of living embodiment of Jupiter himself, so sacrally charged that ordinary contact with iron, death, or the military had to be excluded from his person entirely, while others read the restrictions as evidence of an unusually old priesthood, preserving taboo-based religious logic that most of Roman public religion, generally more focused on correct ritual performance than on personal purity taboos, had already moved away from by the historical period in which Gellius and Plutarch were writing about it as something already unusual and worth explaining to their own readers.