Gernardus

Gernardus was a 13th-century magister (master) and the author of the Latin arithmetical treatise Algorismus demonstratus.

[1][2][3] He belonged to the circle around Jordanus de Nemore at the University of Paris.

[4] His Algorismus was a popular text in the later Middle Ages,[2][5] but largely ignored by early historians of mathematics.

[5][7] A copy was made by Regiomontanus in Vienna, now part of manuscript 5203 of the national library.

[6] On the other hand, he may be identical to another member of Jordan's circle, Gerard of Brussels.