Nice piece on Tesla's longitudinal waves.
Tesla's mistake was not really so big. Especially not a big mistake when compared to those contemporary scientists who were absolutely certain that the Earth *didn't* have any resonant frequencies, who *knew* that radio waves would not travel around the curve of the Earth, and who dismissed Tesla's wireless transmission system as crackpottery; as an unworkable violation of known physics. When "Schumann" VLF earth-resonance was rediscovered in the 1950s, nobody in the conventional sciences dared court the embarassment of admitting that Tesla had been right all along.
Tesla is mostly a hero among the non-scientist "underground," while in conventional circles he is still ridiculed for trying to distribute electric power without using wires, or rather, by sending it through the ground. Everyone (still) knows that this is impossible, even in theory.