The Natural History of Pliny, Volume 6 (of 6)

Daphnea3292 is mentioned by Zoroaster as curative of epilepsy. Diadochos3293 is a stone that resembles the beryl. Of diphyes3294 there are two kinds, the white and the black, male and female, with a line dividing the characteristics of either sex. Dionysias3295 is hard and black, and covered with red spots. Triturated in water, this stone imparts to it the flavour of wine, and it is generally thought to be a preservative against intoxication. Draconitis3296 or dracontia is a stone produced from the brain of the dragon;3297 but unless the head of the animal is cut off while it is alive, the stone will not assume the form of a gem, through spite on the part of the serpent, when finding itself at the point of death: hence it is that, for this purpose, the head is cut off when it is asleep.3298

Sotacus, who tells us that he once saw a stone of this kind in the possession of a king, says that persons go in search of it in a chariot drawn by two horses; and that, the moment they see the serpent, they strew narcotic drugs in its way, and then cut off its head when asleep. According to him, this stone is white and pellucid, and admits of no polishing or engraving.