Louis Poinsot (January 3, 1777 - December 5, 1859) was a French mathematician and physicist. At age 17, he took the ?cole Polytechnique entrance exam and failed the algebra section but was still accepted. He left in 1797 to study at ?cole des Ponts to become a civil engineer, but while there he discovered his true passion, abstract mathematics. He was the inventor of geometrical mechanics, which showed how a system of forces acting on a rigid body could be resolved into a single force and a couple. He devised, what is now known as, Poinsot's construction, a geometrical method for visualizing the the motion of a rigid body on which no external forces are acting. In 1809, he discovered four new regular polyhedra, two of which appear in Kepler's work of 1619, although he was unaware of this. The other two are the great icosahedron and great dodecahedron, some people call these two the Poinsot solids. He was elected Fellow of the Royal Society of London in 1858. He died in 1859 at the age of 82. His is one of the 72 names inscribed on the Eiffel tower.