John Rush

“The effect of hallucinogenic mushrooms on the user's experience and behavior depends in part on his or her personality and genetic predisposition, which can vary to a great extent from person to person. As symptoms of psychiatric disorders can sometimes be elicited after one-off use, people with a genetic tendency to depression or psychosis should be discouraged from using psychoactive mushrooms.”
― John Rush, Entheogens and the Development of Culture: The Anthropology and Neurobiology of Ecstatic Experience

“Inhaling fumes directly from burning foliage, either in a confined space such as a cave or a tent, or scooping up and breathing in the vapors from psychoactive plant materials scattered on a bowl full of hot coals, must be an extremely ancient practice. Herodotus's account from the fifth-century BCE, describing the use of small tents by the Scythians (a northwestern Iranian tribe) for inhaling the smoke of cannabis, is probably the most famous account that confirms the antiquity of the use of cannabis as a ritual intoxicant.”
― John Rush, Entheogens and the Development of Culture: The Anthropology and Neurobiology of Ecstatic Experience