There's a stage in the cycle of growth of the mushroom where it takes the shape of a cup and this has been referred to as the Holy Grail stage. The quest for the Grail itself is apparently the quest for the knowledge of the mushroom. When dew forms on the mushroom or rain collects into this newly formed cup, the water turns red (like blood) and possesses some psychedelic characteristics of the fungi. Historically, the mushroom has been the container for the juice of the ‘elixir of immortality’, or the ‘blood of God’, in many myths. This cup was thought to possess magical powers.
Coincidently, this cup is also used during the Eucharist as it was used during the last supper and is being reenacted in every ceremony: The flesh is the meat of the mushroom, represented by bread, and the blood is the water that magically turns into wine, when poured in the proper cup, represented by red wine. Coincidence?