The incident is related in Etienne-Jean Delécluze's memoirs of David. There is no exact date given but Delécluze places it after Napoleon's coronation, so in the early 1800s. The waxworks in Paris still used the name of Curtius at this time.
David and his pupil Delécluze pay a casual visit to Curtius's premises in the boulevard du Temple and are prevailed upon by Curtius's boy to view a "curious piece". At first they are reluctant, assuming they will be shown something pornographic, but they are assured by the boy that the exhibit will "please them":
|David, self-portrait, 1791|
|Heads, Madame Tussaud Archive|
Some time after 1865
David and Delécluze never spoke of the incident again and Delécluze never recounted it during the painter's lifetime for fear of other people's sarcasm, but he remained impressed by his master's calm dignity in the face of this horrible sight.
Etienne-Jean Delécluze, Louis David, son école et son temps: souvenirs (1855), p.344-5. http://archive.org/stream/louisdavidsonco00delgoog#page/n354/mode/2upDelécluze was generally critical of David's political allegiances which he thought lacked integrity. "This Deep, Great, and Religious Feeling": Delécluze on History Painting and Davidby Marijke Jonker, Nineteenth-century art worldwide, Vol.4(3) Autumn 2005.http://www.19thc-artworldwide.org/index.php/autumn05/209--qthis-deep-great-and-religious-feelingq-delecluze-on-history-painting-and-david