Christian William Anthony Katerfelto (known as Gustavus Katerfelto or Katterfelto) was a celebrated Prussian quack who travelled around Britain from 1776 until his death in 1799.
He performed in London from 1780 to 1784 and gained fame during the influenza epidemic of 1782, when he exhibited his solar microscope in Piccadilly and created immense excitement by showing the infusoria of muddy water.
He was a tall man, dressed in a long black gown and square cap, who was accompanied by a black cat. Such was his notoriety that ‘Katerfelto’ became a generic term name for a charlatan.
And Katerfelto, with his hair on end,
At his own wonders, wondering for his bread.
William Cowper, The Task, ‘The Winter Evening’ (1785)