Shepherd's dial

[1] Its design needs to incorporate a fixed latitude, but it is small and portable.

Since the ancient Roman era, people have created sundials which tell the time by measuring differences in the sun's height above the horizon over the course of the day – Vitruvius describes them as viatoria pensilia.

[2] The earliest description of a shepherd's dial as known today was written by Hermann of Reichenau, an 11th-century Benedictine monk, who called it a cylindrus horarius.

It was also known in the Middle Ages as a chilinder oxoniensis (Oxford cylinder).

Such sundials did not need aligning north-south and so became very popular,[3] appearing in Renaissance artworks such as Holbein's 1528 Portrait of Nicolaus Kratzer and his 1533 The Ambassadors.