Oresme: 

(1320—1382) French philosopher & great original thinker; wrote influential works on sciences & maths, economics, philosophy & theology; Bishop of Lisieux, a translator & counselor for Charles V of France.  He proved the divergence of the harmonic series (which is a divergent infinite series). 

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draughtsmen:

a person employed in making mechanical drawings, as of machines, structures; a person who draws sketches, plans, or designs.

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Non-Euclidean geometry: * see Endnote 24

non-Euclidean geometry traditionally consists of 2 geometries based on axioms closely related to those specifying Euclidean geometry.  Non-Euclidean geometry arises when the parallel postulate is replaced with an alternative. From this modification comes the 2 traditional non-Euclidean geometries: hyperbolic geometry (Lobachevsky-Bolyai-Gauss geometry) and elliptic geometry (Riemannian geometry). Spherical geometry a non-Euclidean 2-D geometry that is a subset of elliptical.  In 1868 Beltrami proved that non-Euclidean geometries were as logically consistent as Euclidean geometry. 

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Numbers:

images of abstract pure thought, whose truth is self-validating, an a priori element