Over 425 Neolithic stone balls with carved knobs have been found in northern Scotland. There is no recorded use of these objects, which has resulted in much speculation about their purpose. In some cases, the symmetry of the knob placements is consistent with symmetry associated with Platonic solids. However, these objects are clearly not polyhedra and thus do not represent examples of Platonic solids, despite recent claims to that effect. Examples are shown along with pictures of modern art that they have inspired. Their symmetric form contributes to their aesthetic appeal, thus they can be considered very early examples of mathematical art.