A Polaroid was a camera that could process photographs instantly. The time traveller Bilis Manger owned an anachronistic Polaroid in 1941. Toshiko Sato used it to take a picture of some of the Rift equations she had so she could preserve them into the 21st century to return home. (TV: Captain Jack Harkness)
The Twelfth Doctor claimed to have taken a polaroid picture of the Tumescent Arrows of the Half-Light. (TV: Robot of Sherwood)