One of the earliest references to tin foil hats and their alleged usefulness in protecting oneself from mind control by an outside force or entity comes from the unusual 1909 non-fiction publication Atomic Consciousness by self-proclaimed "seer" John Palfrey (aka "James Bathurst"). Bathhurst believed such headgear was not effective for his "retention of thoughts and ideas" against a supposed "telepathic impactive impingement". Bathhurst, then, can be considered the first tin foil hat looney on record, although he came to the conclusion that a tin foil hat was not useful. An early mention in science fiction was the short story by Julian Huxley, "The Tissue-Culture King" (1926), in which the protagonist discovers that "caps of metal foil" can block the effects of telepathy. Some folks believe that wearing a tin foil hat will protect them from alleged radio and microwaves being beamed into their heads for purposes of mind control, and there is actually some truth to this. Aluminum is a metal, and blocks electromagnetic radiation to some extent. How much EM is blocked would depend on the thickness of the foil and the strength of the signal.
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