Theriac is being prepared in the presence of a physician. Most doctors believed that theriac and similar preparations produced qualitative changes within the body - by heating or cooling. The fact that it was extremely expensive to produce would not have deterred a rich patient who would despise a cheap drug, however effective.Source: Hieronymous Brunschwig (1450-1551). Liber de Arte Distillandi de Compositis. J Gruninger, Strassburg, 1512.