Engraving from Micrographia, 1665, by Robert Hooke.

Engraving, magnified view of the forms of small diamonds or shining sparks in flints (fig. 1), "the forms of gravel in urine (fig. 2), and a variety of regular for resulting from various combinations of globules (fig. 3, 4)"; Schem. 5. From 'Micrographia: or some physiological descriptions of minute bodies made by magnifying glasses with observations and Inquiries thereupon' by Robert Hooke, Fellow of the Royal Society, 1665.