an icepick through the keyhole

I can't find it right now, but one of the very earliest true photographs (1838) was taken from an attic window in Paris. It shows a 3-street intersection and 3 people who wandered through the long exposure. One is a man walking briskly up the street; he's rather blurry. The others are a man and woman having what must have been an absorbing conversation; they are remarkably clear even though they are more distant