<Table> <Tr> <Td> </Td> </Tr> <Tr> <Td> Logitech spacemouse 3D . On display at the Bolo Computer Museum, EPFL, Lausanne </Td> </Tr> </Table> <Tr> <Td> Logitech spacemouse 3D . On display at the Bolo Computer Museum, EPFL, Lausanne </Td> </Tr> <Table> <Tr> <Td> </Td> </Tr> <Tr> <Td> Silicon Graphics SpaceBall model 1003 (1988), allowing manipulation of objects with six degrees of freedom . </Td> </Tr> </Table> <Tr> <Td> Silicon Graphics SpaceBall model 1003 (1988), allowing manipulation of objects with six degrees of freedom . </Td> </Tr>

An optical mouse and a touch mouse both have 2 buttons