dioptras

Updated: August 18, 2026

For the astronomers Ptolemy Euergetes placed in the Square Porch an equinoctial and a solstitial armil, the graduated limbs of these instruments being divided into degrees and sixths. There were in the observatory stone quadrants, the precursors of our mural quadrants. On the floor a meridian line was drawn for the adjustment of the instruments. There were also astrolabes and dioptras.

John William Draper - History of the Intellectual Development of Europe, Volume I (of 2): Revised Edition