Desargues and Involution

Girard Desargues (1591–1661) is one of the most intriguing figures in the history of mathematics. He wrote a profound and bold booklet on conic sections, in 1639, which might have created projective geometry nearly two centuries before its actual birth. That work was Brouillon project d’une atteinte aux evenements des rencontres d’un cone avec un plan, or A Sketch of a Study of Sections of a Cone by a Plane. Except the work was lost until La Hire’s transcription was found about 1845. Even so, Poncelet knew about involution, an invention of Desargues, when he wrote his 1822 Traite; the Brouillon project had disappeared but letters written in the vitriolic controversary about the work had survived.