In 1936, Blas Pablo Reko, a Mexican ethnobotanist, confirms the existence of teonanacatl as the psilocybin mushroom, refuting the prevailing scientific view of that time that teonanacatl was peyote. Three years later, in 1939, Richard Evans Schultes (a enthnobotany student from Harvard who had joined Reko in his field research) publishes a paper describing teonanacatl as a specific psilocybin-containing mushroom.
Source: Metzner, R. (Ed.). (2005). Sacred mushroom of visions: Teonanacatl. Inner Traditions/Bear & Co.