Title XII of the 1614 book, De exorcizandis obsessis a daemonio, gave the Latin church its ordinary rite of exorcism and prefaced it with rules that remain the heart of the discipline: the exorcist must be a priest of mature virtue expressly authorised by his bishop; he must not readily believe possession is present, but weigh the signs, among them knowledge of hidden things, command of unknown languages and strength beyond nature, against illness and melancholy; and he must avoid all showmanship and conversation with the demon beyond what is necessary.
The rite itself proceeds through the litany, psalms and gospel readings to the solemn imperative prayers commanding the unclean spirit to depart, with the sign of the cross, holy water and the stole laid on the possessed. These pages, kept in Latin even as the rest of the liturgy went into the vernacular, supplied the script that films and novels made universal. The book around them was revised modestly, notably in 1952, and after the Second Vatican Council its contents were recast as separate vernacular rites of baptism, marriage, penance, anointing and funerals issued from 1969 onward, with the Book of Blessings following in 1984; the exorcism title was the last part in force, replaced only in 1999 by De Exorcismis et Supplicationibus Quibusdam, though exorcists may still, with permission, use the old form. The 1614 Rituale thus lives on in fragments, its longest shadow cast by its strangest chapter.