Journal April 1839
p41“Buffon says it is nothing more than a superior aptitude to patience, alluding probably to that brooding, persevering tenacity with which genius clings to its subject matter.”
Fuller, Margaret. "Journal April 1839." Houghton Library, Harvard University; bMS Am 1086 (Box A); Box 5 (99).
Fuller attributes the remark to 'Buffon' by name with no work title; it is a widely-cited oral saying of Buffon's recorded by Hérault de Séchelles (1785).