One of the most famous of these was called Lisbon Diet Drink, which was made of sarsaparilla and mezereon. This latter is Daphne mezereum, a flowering shrub with highly toxic berries - I don't know what the roots are like. It was supposed to have originated with doctors in (not surprisingly) Lisbon, Portugal.
The Art and Mystery of Making British Wines (1865) tells is that it consists of licorice root, sarsaparilla, sassafras, guiacum [a flowering plant also known as lignum vitae) and mezereon. These are all covered with water, boiled and strained. You had to slice everything up, and the recipe makes it sound like it took quite a long time to get everything just right. Even then, some of the plants involved (like the mezereon) sound a bit sketchy in terms of being good for you.
In 1824, one poor fellow, underweight and weak, tried to restore his health with this. He was advised to drink a pint of Lisbon Diet Drink every day "and fumigated his throat twice a day with the red suphuret [sulphide] of mercury." Ouch. That sounds horrible.
Anon., The Art and Mystery of Making British Wines, Cider and Perry, Cordials and Liqueurs (1865), p. 214.
Johnson, James. The Medico-chirugical review, vol. 4 (1824), p. 478.
Parr, Bartholomew. The London Medical Dictionary, vol. 1 (1809) p. 561.
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