I"m only using 10% of my harddrive capacity, too. That doesn't give it processing ability, only storage space. We also KNOW so little about the brain and how much of it can be used as processors versus synapsis pink jello chemical storage.
They are just beginning to discover the effects of specific brain chemicals (and the effects of overloading them). I'm old enough to remember when "Alzheimer's disease" was called senility. It was just accepted as a course of aging, rather than being a condition which was potentially curable--there also wasn't tens of millions in research grant money for senile patients, then, either. You just dealt with it as you watched your father slip into and out of dementia while slowly sliding into the void. Hemmingway had courage, and did what he needed to do--once he tried walking into a turning airplane propeller blade after he discovered that he was senile; that took guts.
Prozac was a dream come true for some, while for others Paxil was a living nightmare (both are essentially the 'same' seritonin re-uptake inhibiitors) by different manufacturers. They, starting with Freud using cocaine continuing with Huxley with mesclaine, and Leary with LSD, have been looking for mind expanding drugs, and haven't found them (not even X, which as I'm sure you know, is little more than LSD and speed combined made without quality controls in somebody's bathtub).
My point? oh, yeah, we just don't know what the brain is capable of, but "newly discovered, previously withheld 'books' about levitation and mental nuclear fission" are most likely frauds to sell books, like von Dannekin's historic spacemen.
So call me Thomas, but show me the holes...