Powder of sympathy was a remedy that by its application to a weapon, which had caused a wound, was supposed to cure or heal the injury.
This method was in vogue during the reigns of James I. and Charles I., and its chief exponent was Sir Kenelm Digby.
An abstract of his theory was contained in an address given before an assembly of nobles and learned men at Montpellier in France may be seen in Pettigrew’s Superstitions connected with Medicine and Surgery.
The following is the recipe for the powder: “Take Roman vitriol six or eight ounces, beat it very small in a mortar, shift it through a fine sieve when the sun enters Leo; keep it in the heat of the sun and dry by night.” This art has been taken seriously by some authors, but not by others. Wrenfels says, “If the superstitious person be wounded by any chance, he applies the salve, not to the wound, but, what is more effectual to the weapon by which he received it.” (see Sympathetic Magic) A.G.H.
Source: 81, 328.