Advertising leaflet for a work entitled 'Cases of successful practice with Perkin's Patent Metallic Tractors', published by George Cooke, London, England, 1801 (see note).

Widely available, these portable devices were used to generate therapeutic electricity in the home or by travelling practitioners. Turning the handles produced an electric current. Damp sponges in the brass cylinders prevented a prickling sensation on the skin. Users and makers claimed the devices could relieve pain and cure almost everything, including cancer and heart disease.