The chapter presets 27 letters from 1870 until 1891 written by Emil Weyr to Luigi Cremona with one letter of František Houdek (from 1873), which are conserved in the "Guido Castelnuovo" Department of Mathematics of "Sapienza" University of Roma. These letters are presented in their original language (French, Italian, German languages) with short biographical notes on Emil Weyr and some historical, cultural, political and mathematical comments.