A review of psychoactive plants known from archaeological contexts and artistic representations shows that their use has spanned centuries, continuing in places in Mexico and South America to the present day. The discovery of the unusual properties of these plants took place as part of the exploration of the physical milieu of the Western Hemisphere. That these plants must in some cases be made into infusions in order to be consumed reveals ancient enterprise in manipulating aspects of the environment. The surprising results obtained from treating psychoactive plants allowed their users to communicate more directly with the unseen world which they believed to exist. It was the great German toxicologist Louis Lewin (1931) who wrote that "from the beginning of our knowledge of man, we find him consuming substances of no nutritive value, but taken for the sole purpose of producing for a certain time a feeling of contentment, ease and comfort." There is ample material proof that narcotics and other psychoactive plants, such as hallucinogens, were employed in many cultures in both hemispheres thousands of years ago. The material proof exists in some archaeological specimens of the plants in contexts indicating magico-religious use and in art forms such as paintings, rock carvings, golden amulets, ceramic artifacts, stone figurines, and monuments.