Anselmus de Boot, physician to Emperor Rudolph II, and one of the great authorities at the beginning of the seventeenth century, gave the following directions for making “_aqua perlata_, which is most excellent for restoring the strength and almost for resuscitating the dead. Dissolve the pearls in strong vinegar, or better in lemon juice, or in spirits of vitriol or sulphur, until they become liquified; fresh juice is then added and the first decanted. Then, to the milky and turbid solution, add enough sugar to sweeten it. If there be four ounces of this solution, add an ounce each of rose-water, of tincture of strawberries, of borage flowers and of balm and two ounces of cinnamon water. When you wish to give the medicine, shake the mixture so that the sediment may be swallowed at the same time. From one ounce to an ounce and a half may be taken, and nothing more excellent can be had. In pernicious and pestilential fevers, the ordinary _aqua perlata_ cannot be compared to this. Care must be taken to cover the glass carefully while the pearls are dissolving, lest the essence should escape.”[362] A curious book on the medicinal use of pearls was written in 1637 by Malachias Geiger,[363] in which he especially praises the efficacy of Bavarian pearls. It was true that their material value was less than that of oriental pearls, but this was compensated by their therapeutic qualities. He had accomplished many cures of a very serious disease and had used these pearls successfully in cases of epilepsy, insanity, and melancholia. Quotations might be given from a hundred medieval writers as to the therapeutics of pearls. The diseases for which they were recommended, as noted by Robert Lovell’s “Panmineralogicon, or Summe of all Authors,” published at Oxford in 1661, seems to have included a large portion of the entire list known at that period. This summary states: