We are told that when Pope Clement VII was seized by his last illness, in 1534, his physicians resorted to powders composed of various precious stones. In the space of fourteen days they are asserted to have given the pope forty thousand ducats’ worth of these stones, a single dose costing as much as three thousand ducats. The most costly remedy of all was a diamond administered to him at Marseilles. Unfortunately, this lavish expenditure was of no avail; indeed, according to our modern science, the remedies might have sufficed to end the pope’s life, without the help of his disease.[477] The old fancy that the diamond grew dark in the presence of poison is explained by the Italian physician Gonelli as caused by minute and tenuous particles which emanated from the poison, impinged upon the surface of the diamond, and, unable to penetrate its dense mass, accumulated on the surface, thus producing a superficial discoloration. The diamond, being a cold substance, may have condensed moisture from the body, and the one suffering from the poison may have emitted exudations. But this elaborate explanation of a phenomenon which never existed except in the imagination of those who related it is characteristic of Gonelli, who was always ready to elucidate in some similar way any of the marvels recounted in regard to precious stones.[478] Emerald The emerald was employed as an antidote for poisons and for poisoned wounds, as well as against demoniacal possession.[479] If worn on the neck it was said to cure the “semitertian” fever and epilepsy.[480] The use of the emerald to rest and relieve the eye is the only remedial use of a precious stone mentioned by Theophrastus in his treatise on gems, written in the third century B.C. Alluding to its powers as an antidote for poisons, Rueus asserts[481] that if the weight of eighty barley-corns of its powder were given to one dying from the effects of poison, the dose would save his life. The Arabs prized emeralds highly for this purpose, and Abenzoar states that, having once taken a poisonous herb, he placed an emerald in his mouth and applied another to his stomach, whereupon he was entirely cured.[482] A certain cure for dysentery also was to wear an emerald suspended so that it touched the abdomen and to place another emerald in the mouth. Michaele Paschali, a learned Spanish physician of the sixteenth century, declared that he had effected a cure of the disease by means of the emerald in the case of Juan de Mendoza, a Spanish grandee, and Wolfgang Gabelchover, of Calw, in Würtemberg, writing in 1603, asserts that he had often tested the virtues of the emerald in cases of dysentery and with invariable success.[483]