In Terry Pratchett's notes for Strata, he mentions various artifacts that have been found and locked away in museums, like a British coin found embedded inside a coal seam. In the start of the story, the main character makes planets, and to create the illusion that this is a natural planet, they will bury dinosaur skeletons to create a fossil record. Only she catches two of her workers trying to bury one holding a sign saying "Stop nuclear testing!" which would spoil the illusion and could cause a culture shock.