Question

What is a pinhole camera? How do we know that these devices existed before the nineteenth century?

Answer 1

A pinhole camera  is a variation of camera obscura which is a simple camera or an optical imaging device shaped like a closed box or chamber. One side of this box would have a small circular hole would would create an image on the outside space on the opposite side of the box through the rectilinear propagation of light.
In Ancient China in 5th century BC, Mozi had mentioned the effect of an inverted image formed through a pinhole. Since then, there had been experiments in ancient China based on the studies made.
The Greek philosopher Aristotle also made an observation regarding the phenomenon in 4th Century BC.
In the 13th century, Robert Grosseteste and Roger Bacon commented on the pinhole camera.