Old physics textbooks give us a great opportunity to learn about the history of science and rediscover different methods to teach physics to our students. There are many disused and forgotten experiments in them, but these can still be very useful to affirm and understand physics. This is the case of an instrument used in the 19th century to demonstrate that the flattened shape of Earth is caused by its rotational motion. Today, this instrument does not appear in textbooks and is not used in secondary school classes. However, there is a modern toy that is identical to it.