 I do not like to have to speak well of myself, but because there are few people who are able to understand my Geometry, and since you will want me to tell you what my own view of it is, I think it appropriate that I should tell you that it is such that I could not wish to improve it. In the Optics and the Meteorology I merely tried to show that my method is better than the usual one; in my Geometry, however, I claim to have demonstrated this. Right at the beginning I solve a problem which according to the testimony of Pappus none of the ancients managed to solve; and it can be said that none of the moderns has been able to solve it either, since none of them has written about it, even though the cleverest of them have tried to solve the other problems which Pappus mentions in the same place as having been tackled by the ancients (To Mersenne, end of December 1637; AT 1, 478; CSMK, 77–78).