NONIUS (Peter), in Spanish Nunus, a learned
Portuguese, and one of the ablest mathematicians of
the 16th century, was born at Alcaçer. He was pre-
ceptor to Don Henry, king Emmanuel's son, and
taught the mathematics in the university of Coimbra.
He published the following works, by which he gained
great reputation: 1. De arte navigandi. 2. Anno-
tationes in theorias planetarum Purbachii; which are
greatly esteemed. 3. A treatise De crepusculis. 4. A
treatise on algebra. It is observed in Furetiere's dic-
tionary, that Peter Nonius, in 1530, first invented the
angles of 45 degrees made in every meridian, and that
he called them rhumbi in his language, and calculated
them by spherical triangles. Nonius died in 1577,
aged 80.