"Mankind has measured the passing of time using the apparent movement of the sun since before 1500 BC using a number of different instruments.
The dial dates back to around 300 BC, when a hollow hemispherical instrument was first used.
Portable versions came into existence soon afterwards. They relied on the altitude of the sun rather than its direction, needing a correction for the time of year. Later versions also incorporated adjustments for latitude. During the 15th century the development of the magnetic compass made a portable sundial possible, because the operator could know the direction of North. "
Supplied in a box measuring 4" square, 2½" tall.