What exactly did apothecaries think had curative powers in medieval times? Precious and semi-precious stones like agate were thought to cure eye problems; mineral water which is still believed today to have curative powers; products from animals (quite a big trade still exists in China today of different animal parts, some which result in the cruel slaughter of endangered species, often just to harvest their fins, tusks, or other organs); products from humans such as nails, urine, blood; spices; and a large variety of dried plants and mushrooms.
Because convents, monasteries, and abbeys were places of learning, could afford to purchase expensive hand-illustrated and written one of a kind books, and had special gardens called herbularius dedicated to medicinal plants called simples, they received the pilgrims and the poor who were offered hospitality within the abbey, in a wing called hospitals; the monks often treated their sores, ailments, and diseases for the duration of their stays. The monks were the teachers, the herbalists, the apothecaries, the doctors of first resort, and spiritual guides.
A pharmacopoeia, De Materia Medica, by the Greek physician Dioscorides, was found in monasteries in the medieval west as well as in the Arab world. A pharmacopoeia was a compendium published as an authority for standards of strength, purity, and quality of therapeutic drugs. It described how each drug, potion, and poultice were formulated, their chemical properties, quantities, and preparation methods so that the resulting product would be ‘standard’ every time. Today we have the U.S. Pharmacopoeia (USP), the European Pharmacopoeia (EP), and the British Pharmacopoeia (BP).