Question

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

Answer 1

Pinhole cameras are objects that have a pinhole camera embeded into them. The size of the pinhole is just as what it says. However, the standard term suggests that a pinhole camera lacks a lens, and a single small aperture. They have existed long before the 19th century, as it was used mostly for undercover and/or general surveillance.