Some of this stuff popped up about the time a guy named Selig (from Indianapolis) went from Naptown to Brazil to assist in setting up an enormous developmental effort in the jungle.
I've subsequently discovered that a guy named Carvalho/Carvajal (same name, one Spanish, one Portuguese) made the first trip down the Amazon by starting over in the Andes, and then made his way to the plains in what is now Southern Ecuqador, etc., and moved from there (with some companions) to the East Coast. He had a diary which no one ever paid any attention to until recently. I'm betting Selig was simply the first guy to believe that diary. This is where all the stories of folks with blond hair come from. He also said there were large cities out there with hundreds of thousands of people. More recently another Carvajal has been using the older information as a guide to find massive settlements ~ and he's been finding massive settlements (or rather, their raised bed farms, still there).
I had a female engineer (Zulma) from Peru in my organization years ago and asked her about the blonde headed people I'd heard about. She said, "yes, they're there in the mountains".
Here's what I found about the mushrooms.
"Perhaps no other ethnobotanical is more shrouded in mystery and intrigue than the Amanita Muscaria mushroom. Some scholars have suggested that the Viking berserkers ate the mushroom before battle to enter a frenzied state. Others have claimed that it is the legendary intoxicant Soma, worshipped as a God by early Hindus. In Western culture, it is the mushroom of fairy tales, a symbol of both poison and magic. For generations, the tribal shamans of Siberia and the Pacific Northwest have ingested Amanita Muscaria to enter Altered States of Consciousness."