Also since the earliest times, people have exploited some of the many psychoactive substances manufactured by plants in religious rituals and for pleasure.[34] Among the most widely used throughout history are alcohol, produced by fermenting cereals with yeast (a fungus),[35] tobacco, coffee, tea, chocolate, cannabis, coca (used as leaf for some 8,000 years in Peru,[36][37] and in recent times also purified to cocaine), mescaline (from a cactus) and psilocybin (from a fungus).[38]