The Stone Operation. There
was an old Dutch saying for a person of odd behavior that he had 'a stone
in the head'. Trading on credulity of simple people, charlatans would offer
to extract stones. They always found patients among those with headaches.
The 'surgeon' would then tie his patient safely to a bench, make a small
cut and under cries, moans and groans of the victim produce a pebble or
two covered with blood. These 'surgeons' were a popular object of satire
in the 17th century.