Isaac Newton proposed in 1697 that the rotation of the earth would cause the poles to flatten in comparison a perfect sphere, but at the time his work was not quickly adopted outside of England.

Emelie du Chatelet made some of the first translations of Newton's work into French, and to be fair, she did more than translate. She cleaned up the notation, and added commentary of her own. Voltaire was her lover, but in 1733 they were on a break when she hooked up with Pierre Louis Maupertuis.

In the times that they were out of bed, they talked about math and astronomy, and eventually he put together an expedition to Lapland in order to measure how much flattening there was. He found that the poles were 191 meters closer to the center of the earth than the equator. More modern measurements put the figure at 298m.

Source "Passionate Minds: Emilie du Chatelet, Voltaire, and the Great Love Affair of the Enlightenment" by David Bodanis. p 73, 104.