The button mushroom you buy in the store is considered safe enough, but often everything else is lumped together as a toadstool. This photograph by Kit Scates Barnhart shows one of the classical toadstools, Amanita pantherina, or a close look-alike that is indeed toxic, though the toxins are not related to it having been sat upon by a toad as was once believed. In addition to some most unpleasant effects, the water soluble toxins cause changes in perception of time and of size and so some people consume this mushroom intentionally to get high. Others boil it and throw away the water or can it and then discard the liquid and then use it in cooking. However, not getting rid of all of the water leads to unpleasant surprises including agitation, muscle spasms and deep coma-like sleep.
Recovery is generally complete on the following day but the hospital bill can be significant.