Use of ayahuasca for visionary experiences appears to be primeval, to judge from the richness of associated mythology. Pre-Columbian rock drawings are similar to contemporary ayahuasqueros' paintings, which are said to represent yage visions (see page 127 of Plants of the Gods for a fine example of such a drawing on granite). However, the earliest known record of the practices associated with this botanical wasn't set down until the middle of the nineteenth century. Four or five half-foot pieces of bark from a medium-sized vine (an inch or two inches of thickness) are often provided per person in yage brews. Estimates of dosages presented here are rough, being generally based on experiences in the field rather than in the laboratory. These vines have now become relatively rare in their native jungle growing area, so genuine yagé is rarely seen. (Several people who have searched for it report that a decent ayahuasquero is hard to find these days; many have given in to "alcohol abuse".)