The Universal Antidote is a mixture that contains activated charcoal, magnesium oxide, and tannic acid. All three components neutralize the actions of many poisons. It is prepared by mixing "of two parts activated charcoal, one part tannic acid, and one part magnesium oxide intended to be administered to patients who consumed poison. The mixture is ineffective and no longer used; activated charcoal is useful." It is now believed that activated charcoal and water is just as effective.
Tar water was also suspected to be a panacea due to its seemingly universal effects.