Men of the Borgian Era knew that the tail of an ibex, dried with its flesh and skin and worn about the person, would ward off magic unless the wearer should consent thereto. This they learned from St. Hildegard’s treatise _De Animalibus_. They knew that the herb Heliotrope or Turnsole (_Heliotropion Europaeum_), placed under the pillow of a man who has been robbed, will bring him a vision of the thief and his spoil; and that, when it was set up in a church, unfaithful wives would be unable to go away until it was removed. Their faith in the virtue of gems was very precious; and chiefly derived from the physician Alexandros of Tralles. A cockatrice engraved on green jasper preserved from the Evil Eye. A metal cross tied on the left arm cured epilepsy. A live spider tied in a rag on the same arm cured ague. A metal ring, engraved with the sacred tau =Τ= (the “_Mark on the Forehead_”), also freed from epilepsy. A ring, set with ass-hoof, cured ἀδυναμία. A ring, carved with a council of ravens for Apollo, conferred conjugal joy and the gift of clear-seeing. A brownish-yellow jacinth gave sleep. An agate, carved with St. John the Divine, protected from venom. Oriental jasper or heliotrope (blood-stone), engraved with a youth wearing a necklace of herbs, when anointed with marigold juice, conferred invisibility. A copper ring, figured with a lion, a crescent, and a star, and worn on the fourth finger, cured calculus. Amethyst kept the wearer sober, and a papal bull ordained it for episcopal rings. Coral delivered from incubi and succubi. Herakles strangling the lion of Nemea, carved on a honey-coloured sard, cured colic. Carnelian carved with a Hermes Psuchopompos gave cheerfulness and courage. A man might live as long as he liked if he looked at a presentment of St. Christopher (the Christian Herakles) every day.[72] The toad-stone or bufonite (the fossil palatal tooth of the ray-fish _Pycnodus_) when set in a ring was a most potent periapt against black magic. In the University Galleries at Oxford, No. 691, there is a splendid specimen of a double-toad-stone ring; _i.e._, the stones are set outward on opposite sides of the ring so that the one always touches the closed hand, while the other is free to dismay a magical enemy. Cheiromancy was expounded by Messer Andrea Corvo da Carpi, whose deeply religious little treatise adorned with diagrams was published at Venice in 1500.