The Halley's Comet Panic of 1910, When Earth Passed Through the Tail and Con Men Sold Comet Pills
Astronomers announced that on 18-19 May 1910 the Earth would pass through the tail of Halley's Comet — and that the tail contained cyanogen, a poison. Amplified by newspapers and a famous astronomer's speculation, the news spawned sealed rooms, comet pills, and gas masks. Mark Twain, born under the comet in 1835, died as it returned — as he had predicted.
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