Oldest compass invented was a magnetic compass. Its first role was to help people find precious stones and build houses according to feng shui. It took centuries for it to be used properly - as an instrument for navigation and to help people not to get lost while exploring seas and lands.
Magnetic compass was at first used as a magical artifact and a tool for divination. It took centuries for it to be used for its proper purpose and to change the world as we knew it.
Despite the simplicity of a compass, it took hundreds of years for it to be discovered and some more hundreds of years to be used for navigation instead as a magical artifact. But when we began to use it properly, it changed the face of the Earth.