A great mushroom myth I heard relates back to the days of the Christians' Exodus from Egypt. Supposedly, while wnadering through the desert, the poor bastards encountered 'manna from heaven'.
*disclaimer: author is recalling this from freshman year, and many holes have been burned into memory since then*
tribes back in those days probably stayed away from mushrooms, especially displaced tribes like the enslaved Christians, who would not have herbal/fungal knowledge, since they were used as common laborers. The 'manna', which means "bread from heaven" would show up every morning on the ground. Moses instructed (or WAS INSTRUCTED, OOOOO) the Christians to take only what they need for a single day. Those that broke this rule and tried to hoard the manna found it rotting the next morning. The Bible also speaks of the visions this manna brought the wanderers, thus insuring that it was truly given by God to his Chosen.
The myth that I read continued the supposition by relating circumcision to this instance. Supposedly, each male (post circumcision) now had his very own 'mushroom' to remind him of the pact that Abraham and Moses had with The Lord -- who actually sent down food for them, proving his existence!!
umm...rereading this makes me realize that I have my chronology wrong. The people enslaved by the Egyptians would have been early Jews, not Christians. Moses was, after all, before Christ.
CMB, definitely do some research in the Lycaeum and the Shroomery. I used to haunt over there and I'm sure a search on 'circumcision' would yield this story.