I have been trying to source a famous quote of Descartes, "Omnia apud me mathematica fiunt." or "With me everything turns into mathematics."
I cannot find a source for this. The English e-books I have, nor the the Latin version on Google books.
It's scattered all over the web and "turns into mathematics" shows up in Google's N-Gram viewer starting in 1930. None ever cite the book it came from, let alone the chapter.