The Torus: a compact, oriented 2D-manifold with genus 1

The Torus a compact, oriented 2D manifold with genus 1 by AltDynamic — Kickstarter
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Affectionately nicknamed the "donut", the venerable Torus is the cousin of the degenerate Sphere. The ancient Greek (300 BC) mathematicians Euclid, Archimedes and Proclus are normally credited with discovering the Torus (though they did not specifically point it out). Centuries later, academics from Rene Descartes, Leonhard Euler, Felix Klein, John Nash and Albert Einstein would all be required to use the Torus to help discover Calculus, push the limits of Topology, Partial Differential Equations and General Relativity.