Well, they are pills made from... dried frogs.
Dried frog pills are a magical medicine, and as you might expect, they are a hallucinogen. They were introduced to us in Terry Pratchett's Discworld novels, where they are best known for being used by the Bursar of the Unseen University.
These pills are carefully concocted, and the Bursar's recipe is unknown to us; the effect, however, is well known, and quite desired. The pills manufactured at the Unseen University will make the user hallucinate that he or she is sane, with the side effect that they will often actually act as if they are sane. In the Bursar's case, he also hallucinates that he can fly; generally he does not have reason to test this belief, but for obvious reasons dried frog pills are contraindicated for those living in mountainous areas or in any apartment above the ground floor.
While the University's meticulously formulated pills involve carefully selected and very poisonous frogs killed in quite specific ways, carefully dried, and mixed with only the most select ingredients (so as to prevent unwanted explosions), there are other recipes. Nanny Ogg's Cookbook contains a simple recipe:
You will need:
Whisk egg white until stiff. Gradually beat in the sugar and cinnamon. Add rum flavoring and food coloring and mix well. Roll the mixture into pea-sized balls and place on waxed paper for 8 hours to set. (Most experts find that the tablets resulting from this recipe are improved if you substitute the
frogs with
no frogs.)
It is generally held that dried frog pills are not addictive (if they were, such an apparently sane and wise man as the Bursar surely wouldn't keep taking them), but it is wise not to exceed the recommended dosage. The recommended dosage is unknown, but suffice to say, sane people do not take dried frog pills. Let this be your guide. And if in doubt, try topping off your dose with an extra dram of rum. Repeat until the doubt subsides.