Courtois' drawings were, even in his lifetime, very much sought after, Cardinal Léopold de' Medici, after Courtois' departure from Florence to Rome, unsuccessfully tried to acquire a battle drawing. The reason of the rarity of Courtois' drawings was that he hardly ever drew compositions: he wrote in a letter to Alberto Vanghetti, a dealer from Bergamo, that 'non soglio fare disegni finiti, ma solamente schizzi', A.M. Guidicci, A propos de quelques dessins du Bourguignon in La Donation Baderou au musée de Rouen, Paris, 1980, p. 37.
At the time of Courtois' death, he left an album of 72 drawings to the Jesuits, which was directly bought by Pietro Bellori for seventy scudi romani. Anna Maria Giudicci suggested that the drawings marked with a cross come from this group. A large number of these are in the British Museum and in the Louvre. Another theory is that the cross was placed on the drawings by Courtois himself after he joined the Jesuit order.