Vorlesungen über Natürliche Geometrie

This is the gold standard in books on Plane Curves etc, and their analysis using Intrinsic Coordinates. It opens doors that weren't known to exist heretofore. Cesaro has shown his knowledgae of other European authors, who have dabbled in Intrinsic Coordinates for a special purpose, but then Cesaro extends all their findings and adds a plethora of his own.
The mathematics is translated exactly by Gerhard Kowalewski into a German translationn about 1906, bu then about 20 years later Kowalewski wrote a book on Lie Groups using all of Cesaro's maths. but this time the presentation of the maths is better and more rigorous and lucid display of the methods of that later era. I put him and Kowalewski on the same highy pedestal of great mathematicians.
David Halprin