Arcanum duplicatum (potassium sulfate), also known as panacea duplicata, in pre-modern medicine, it was used as a diuretic and sudorific.
The recipe was purchased for 500 dollars by the Duke of Holstein. Schroder, the prince's physician, wrote wonders of its great uses in hypochondriacal cases, continued and intermitting fevers, stone, scurvy, etc.
References
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