The clay tablet is part of a guide to exorcising ghosts held in the collections of the British Museum, reports Dalya Alberge for the Observer. Irving Finkel, a curator in the London museum’s Middle Eastern department and the author of the forthcoming book The First Ghosts: Most Ancient of Legacies, says the image on the tablet is only visible when viewed from above under a light. The museum acquired the artifact in the 19th century, but it has never been exhibited.