Of all the mushrooms found on earth this is the most iconic, seen in every fairy tale book and pictured in every outdoor book. The red and white fungi is very striking and not easily confused with anything else
Although classed as poisonous it rarely ever caused death through ingestion needing around 14 caps of concentrated muscimol for a fully grown adult.
It's well documented about shamans using this after being filtered through reindeer urine but an even more interesting lecture was presented by Thomas J Reidlinger in 1999 to the Mycomedia millennium conference where he postulates that it was fly agaric that caused the warp spasms of the Ulster hero CuChulainn.
If you can get a hold of his presentation it makes remarkably interesting reading.