Two fabulous stones are noted by pseudo-Aristotle, and one of these, the “sleeping-stone,” must have possessed marvellous soporific power. It was a luminous stone of a bright ruddy hue, and shone in the darkness with a bright light. If a small quantity of this stone were hung about a person’s neck, he would sleep uninterruptedly for three days and nights, and, when awakened on the fourth day, he would still be almost overcome by sleep. The other stone, of a greenish hue, had the opposite quality and induced prolonged wakefulness; so long as it was worn, sleep was banished. Our author gravely states that “some men who must watch at night suffer greatly from lack of sleep.” If, however, they wore the “waking-stone,” they suffered no inconvenience from their enforced vigils.[243] Evidently this stone would be a precious possession for night-watchmen, and a more satisfactory guarantee for their employers than “timeclocks” or other tests of wakefulness. In his commentary on Marbodus, Alardus of Amsterdam relates the history of a wonderful luminous stone, a “chrysolampis,” which, with many other precious stones, was set in a marvellous golden tablet dedicated to St. Adelbert, apostle of the Frisians and patron of the town of Egmund (d. 720-730), by Hildegard, wife of Theodoric, Count of Holland. The gift was made to the Abbey of Egmund, where the saint’s body reposed. Alardus tells us that the “chrysolampis” shone so brightly that when the monks were called to the chapel in the night-time, they could read the Hours without any other light. This wonderful stone was stolen by one of the monks, whom Alardus terms “the most rapacious creature who ever went on two legs”; but, fearing to keep so valuable a gem with him, he cast it into the sea and it was never recovered.[244] Strange tales were told of a luminous “carbuncle” on the shrine of St. Elizabeth (d. 1231) at Marburg. This stone was set above the statuette of the Virgin, and it was said to emit fiery rays at night. However, Creuzer informs us that it was only a very brilliant rock crystal of a yellowish-white hue. The shrine was an elaborate work of art in silver gilt, and was literally covered with precious stones to the number of 824, besides two large pearls and a great many smaller ones. All these gems were stripped from their settings when the shrine was taken from Marburg to Cassel in 1810.[245] At the Dusseldorf Exhibition of 1891, the writer saw what was called “The Ring of St. Elizabeth,” purporting to be set with her miraculously luminous ruby. The stone in the setting proved, however, to be a large almost flat carbuncle garnet of no great brilliancy, set in a narrow rim of gold.