And what horses! His sources range from the highest echelons (Caulaincourt, at Napoleon’s side), to the rank and file (the author’s own choice of lowlier men being ‘obscure little Swiss voltigeur Jean-Marc Bussy’). My only quibble on this score is that it's not always completely clear who's being quoted.
 Given how much time Caulaincourt spent in close proximity to Napoleon, it's amazing how hard it is to find any contemporary images of them together!
 If pictures of Caulaincourt with the Emperor made me think of him as the invisible man, then what should I call poor old Jean-Marc Bussy? I could find no images of him at all. So instead I found some pictures by Carle Vernet, illustrating uniforms of the 1812 regulations (which Vernet also had a hand in designing). These guys playing footsie with each other look to be having an easier time of it than Bussy had! I did, however, find out that Bussy later became a police-man, and lived to the ripe old age of 88!
... then, a bit later, I found the picture below, by Knötel. This one has a Swiss Voltigeur, on the right. I guess Bussy must've looked something like this fellow?