I was reading Reddit for
sources on medieval or early use of mushrooms and found the author, but mentinoing only A. Muscaria. This thread comes up when searching for 'Wasson'.
My initial hypothesis was that mushroom use was associated with witchcraft, but it seems the severity of religious persecution at that time
can make the mushroom use more or less irrelevant. One could have experienced serious ramifications in public perception just for being associated with the wrong people or art or literature.
Altogether, I did minimal research on the author, but it seems he is one of the few good sources for early use of psychedelics.