The name "camera" comes from camera obscura, which means "dark room." Used as an early drawing aid, the artist would stand in a light-sealed room or box with a hole punched in it. Light would enter through this hole and form an inverted image on the opposite wall, ready to be traced onto paper.
Later, film and lenses were added, and then--later still--CMOS sensors and iPhone apps. But you can go retro today with Justin Quinell's Camera Obscura kit.
The kit consists of a lens, a big (1.8 x 1.6 meter) projection screen, a smaller handheld screen and velcro. Once you have blacked out your room, you put the lens over a hole in the material covering the window, position the screen about 90cm (three feet) behind the lens and switch off the lights.
Once your eyes have amped up their sensitivity, you'll see the inverted image on the screen. You can also hold up the smaller translucent screen and see the image framed from the back. It'll still be upside-down, though*.
Quinell's kit can be had for $25, which is a bargain for something that contains "2500 years of optical wonder." Or you can just make your own, and Quinell provides free how-to instructions for that.
Either way, this is an experiment that is certainly worth doing. Especially if you have kids, who likely believe that every gizmo need to be plugged into the wall to do anything interesting.
Camera Obscura Kit [Pinhole Photography via PetaPixel]
*Question: Why does a mirror reverse from side-to-side, but not top-to-bottom?
