Adam Ries

Adam Ries was a mathematician from Bad Staffelstein in Bavaria. Ries lived in the 16th century. He was born in 1492 or 1493, and died in 1559.
Ries became known for a work on how to calculate. His first work was about a "calculating board", which was widely used at the time. It worked rather like an abacus. Ries showed that Roman numerals were impractical for calculation.
Ries wrote in German, and not in Latin, as orher mathematicians of his time.