What did Elisha Perkins claim his metallic tractors could do?

Elisha Perkins, a figure associated with quackery, claimed that his invention, known as "metallic tractors," could draw disease out of the human body.1

These devices consisted of two small rods—one made of brass and iron, and the other of copper, zinc, and gold—which Perkins marketed by exploiting public interest in the then-recent discovery of electricity. Despite costing only one shilling to manufacture, the rods were sold for $5.00, serving as a clear example of a charlatan making exaggerated medical claims for financial gain.1