England: Euclid holding a sphere and dioptra observing the moon and stars; Hermannus holding an astrolabe. Coloured drawing, Liber Fortunae, Bernardus Silvester, late 14th century

Euclid (fl. 300 BCE), sometimes called Euclid of Alexandria to distinguish him from Euclid of Megara, was a Greek mathematician, often referred to as the 'father of geometry'. He was active in Alexandria during the reign of Ptolemy I (323–283 BCE).

Hermann of Reichenau (July 18, 1013 – September 24, 1054), also called Hermannus Contractus or Hermannus Augiensis or Herman the Cripple, was a Roman Catholic 11th-century scholar, composer, music theorist, mathematician, and astronomer. He built musical and astronomical instruments and was also a famed religious poet.

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