Erik Vance in Aeon:
Some trace the first hypnotists back more than 4,000 years to the sleep temple of the Egyptian priest Imhotep; others to ancient Greece. The original source of the induction techniques familiar today is probably the Roma, or Gypsies, who would have brought hypnosis from India to Europe 1,000 years ago. The modern incarnation of hypnosis can be traced to the 18th-century German priest and exorcist Johann Joseph Gassner, who believed he had the power to channel God’s word through his own voice. By speaking in a calm and commanding tone to his patients, he could reportedly rid them of all sorts of demons that today we might call epilepsy or muscle spasm. In one case, he is said to have commanded a patient to slow down his pulse in one arm while speeding it up in the other. Gassner’s work was spotted by Franz Mesmer, a German gentleman scientist who theorised that magnetism controlled the tides (it doesn’t), planetary movement (it doesn’t) and even health (it really doesn’t). He wore a striking silk coat with a silk liner to keep his magnetic power in, and would often carry an iron rod to wave over people, or treat them using small magnets.
…Mesmer’s most famous client was Marie Antoinette. Her husband Louis XVI at first welcomed Mesmer to Paris but soon became suspicious and formed a panel of eminent scientists – including Antoine Lavoisier, the father of modern chemistry, and Benjamin Franklin, one of the founding fathers of the United States – to evaluate Mesmer’s techniques. The result was a wonderfully entertaining scientific treatise that discredited Mesmer’s magnets and foretold the era of placebo-controlled trials. But the team also sent a secret memo to the king, pointing out that a person under the power of hypnosis would be easy to sexually assault.