A certain king had three sons and one precious stone. When the hour of his death had come, he reflected that his sons would dispute for the possession of the stone. Now he loved one of his three sons better than the others, wherefore he caused three similar rings to be made and two glass imitations resembling the precious stone; he then had the three stones set in their respective rings. Lest his plan should fail, the father called his three sons to him, and gave to each the ring destined for him, giving the best one to the son he most loved. After the father’s death each of the sons declared that he had the ring with the precious stone. Hearing this, a sage said: “Let us make a test, for that ring which can cure disease is the most precious.” The test was made, and two of the rings had no effect, but that with the precious stone cured the disease; whence it became manifest which of the sons had been best loved by his father.[571] It was this mediæval tale that suggested to the German dramatic poet and critic, Lessing, the celebrated parable of the three rings, which he puts into the mouth of Nathan the Sage,[572] in answer to Saladin’s question as to whether the true religion was Judaism, Christianity or Mohammedanism. Nathan likens them to the three rings given by the father to his sons, the secret as to which was the genuine magic ring being hidden from them. Pursuing the parable, he makes the sons, after the father’s death, bring their dispute before a court of justice. The judge having heard the testimony, at first declares that it is impossible for him to determine which of the rings is the genuine one; then, after a moment’s thought, he recalls the statement that the hearts of all will be drawn toward him who has it, and asks which of the brothers is most loved by the other two. They are honest enough to confess in turn that each loves himself the best. Thereupon the judge adjourns the case for a few thousand years, during which the race that has shown the greatest virtues will become the favored one, and thus prove that its ring was the true one. Mediæval superstition did not shrink from the belief that some magicians had such power over the spirits of evil that they could force a demon to take up his abiding-place in a ring, and rings of this kind were thought to be powerful medical amulets. In classic times also medicine-rings were known and used, one having been given by Augustus to his son-in-law Agrippa.[573]