'Loopt Loopt Met Groot Verblyden, Hier Salmen twyf van Lije Snyden', 17th century. This image shows a quack doctor about to make an incision in a woman's head to remove the stones that are supposedly embedded within it. This was a popular subject matter in late 16th and early 17th century prints in the Netherlands and mocked the gullibility and simple nature of village people. Stones in one's head was seen as the cause of stupidity and a number of other ailments. This is where the English idiom 'rocks in the head' comes from.