In Middle-Ages Europe, especially in the Northern part, devoted people would often carry a prayer nut, an item that could be kept for praying anywhere. The object get its name from its appearance, it looks like a nut, and would often reveal details carvings, like in the pictures in this post. Some aromatic fragrances would often be inserted in the nuts, adding an extra touch to the religious experience.
The nut pictured here can be seen at the History and Art Museum in Vienna. More pictures can be seen on Campra’s photostream on Flickr.