Like Freemasonry today, only men were allowed to be initiated into the Mysteries of Mithras. By the 3rd century A.D., seven grades or degrees of initiation were recognized - three lower degrees and four higher degrees. Each degree was associated with a planet and certain symbols as follows:
Grade Planet Symbols Mosaics from Mithraeum of Felicissimus at Ostia Antica Near Rome
1.  Corax (Raven) Mercury Beaker, Caduceus
2.  Nymphus (Bridegroom) Venus Lamp, Diadem
3.  Miles (Soldier) Mars Pouch, Helmet, Lance
4.  Leo (Lion) Jupiter Batillum, Sistrum, Thunderbolt
5.  Perses (Persian) Moon Akinakes, Scythe, Moon and Star
6.  Heliodromus (Sun-Runner) Sun Torch, Radiated Crown, Whip
7.  Pater (Father) Saturn Patera (or Ring?), Staff, Phrygian Cap, Sickle


The above seven degrees are known from only one written source, the Christian priest and translator of the Vulgate (Latin) version of the Bible, Jerome (347-420 A.D.). In an epistle known as a "Letter to Laeta" Jerome writes as follows:

" ... did not your own kinsman Gracchus, whose name betokens his patrician origin, when a few years back he held the prefecture of the City, overthrow, break in pieces, and set on fire the grotto of Mithras and all the dreadful images therein? Those I mean by which the worshippers were initiated as Raven, Bridegroom, Soldier, Lion, Persian, Sun-Runner, and Father? Did he not send them before him as hostages, to obtain for himself Christian baptism? ... "