- Christoph Clau
- Euclid of the 16th century
Jesuit astronomer and mathematician. Known as the Euclid of the 16th century, he distinguished himself in mathematical research at Coimbra and was appointed to the chair of mathematics at the Collegium Romanum. He devised a method of dividing a measuring scale which was the precursor of the so-called Vernier’s measuring instrument, but his greatest achievement was the execution and success of the Gregorian Calendar reform which prevailed through his efforts. His numerous scientific works have been published collectively under the title of . Among them are a practical geometry and algebra, an exposition of gnomonics, and a treatise on the Gregorian Calendar reform.