Horizontal Pocket Sundial

In the antiquity the movement of the sun in their journey from east to est constituted a rudimentary clock, this immense clock moved neither forward or backwards. The clock needed a tangible mechanism that allowed it to differentiate time with some precision in rhythmic succession of the natural phenomenous. It was this mechanism the solar gnomon. With a rod place into the ground and the sun shinning on it, a line was thrown by the shadow. At the same time, as the sun made its projection in a eclipsed movement, the rod’s shadow change its length and position.

This primitive apparatus was used by the Babylonians, Chinese, Egyptians and the Peruvians. The great obelisk in the Concorde Square in Paris, Saint Peter’s square in Roma and the Hippodrome in Constantinople are no more than ancient solar gnomon.

One popular portable sundial design was called a diptych. It consisted of two small flat faces, joined by a hinge. Diptychs usually folded into little flat boxes suitable for a pocket. The gnomon was a string between the two faces. When the string was tight, the two faces formed both a vertical and horizontal sundial. The best material was white ivory, inlaid with black lacquer markings. The best gnomons were black braided silk, linen or hemp.

Large (meter-sized) diptychs may have been used for navigation in ancient time.