In medieval Europe, fossilised ammonites were thought to be petrified coiled snakes, and were called snakestones or, more commonly in medieval England, serpentstones. They were considered to be evidence for the actions of saints, such as Hilda of Whitby, a myth referenced in Sir Walter Scott's Marmion, and Saint Patrick, and were held to have healing or oracular powers. Traders would occasionally carve the head of a snake onto the empty, wide end of the ammonite fossil, and then sell them as petrified snakes. In other cases, the snake's head would be simply painted on. Ammonites from the Gandaki River in Nepal are known as saligrams, and are believed by Hindus to be a concrete manifestation of Vishnu.