Not necessarily psychotropic mushrooms. To learn more about them, read Andy Letcher’s Shroom or the works of Paul Stamets, Dale Pendell, etc.

These are metaphorical mushrooms—or mushrooms as metaphor—from an article by Wouter Hanegraaff on the German scholar of esotericism Will-Erich Peuckert (1895-1969):

To me, [Peuckert’s] book [Pansophie] breathed  an unmistakable mycological atmosphere: the mushrooms I used to collect during my trips through the forest, and the strange ideas and personalities that Peuckert had collected during his forays through the tangled woods of early modern history, simply “smelled” the same. The effect of the book had a lot to do with Peuckert’s inimitable prose … by which he introduced his readers to a forgotten world that seemed to be suffused with the same mysterious atmosphere of magic and fairy tales which, to me, had always given mushrooms their special attraction. Whereas green plants, trees and flowers flourish in broad daylight for all to see, mushrooms were half-hidden creatures of twilight, ambiguous and potentially poisonous plants-that-are-not-really-plants (what were they, really?) associated by popular tradition with the forbidden domains of magic and witchcraft. In short, mushrooms might be defined metaphorically as the occult in biology—and conversely, one could say that Peuckert now introduced me to what seemed like the mushrooms of history. Just as mushrooms grow in the autumn and are thus associated with decay and the decline of the life cycle, Peuckert described the magic of the fifteenth and sixteenth centuries as the final flowering of a grand worlview in decline, inevitably doomed to be dissolved by the rise of bourgeois culture.

Wouter J. Hanegraaff, “Will-Erich Peukert and the Light of Nature,” in Esotericism, Religion, and Nature, ed. Arthur Versluis, et al. (Minneapolis: Association for the Study of Esotericism, 2010), 282-83.