The London optician John Cuff (ca. 1708-1772) can be considered the inventor of the heliostat. He used it, in combination with a solar microscope after the German physician and naturalist Johann Lieberkühn (1719-1769) had introduced his microscope without a mirror in England in 1740, followed by much argument.
Cuff's model had the tube of the microscope fixed to a circular aperture made in a window by means of a wooden frame which had on the outside a disk which, in turn, held a flat rectangular mirror which was inclined.
From the inside of the room it was possible to rotate the disk and regulate the inclination of the mirror so that the sunlight was always directed into the microscope tube.
In this configuration, with the simple substitution of the wooden frame with a metal plate and slight adjustments of the mechanisms for rotating the mirror and adjusting its inclination, the heliostat was widely used in the 18th and 19th centuries.