Popular in the 17th century, this was a remedy used by doctors treating soldiers. According to the instructions for making it, you should first obtain six to eight ounces of Roman Vitriol (copper sulfate, CuSO4, now used to destroy algae in lakes, ponds, reservoirs, etc.). Next, grind this up (using a mortar and pestle) and use a fine sieve to sift it when the Sun enters Leo. Finally, you must keep it in the light during the day and make sure it stays dry at night.
The curious thing is that according to the directions, if you were wounded, you do not apply this powder to any wounds, nor do you swallow it. Rather, you apply it directly to the weapon that caused the wound. At the time, there was much debate over its effectiveness.