Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       artefacta - artefacts
         Product group devices
           Product group machines
             Product calculator
               Product mechanical calculator
                 1 Product Antikythera mechanism ca. 100 BC
                 2 Product Pascal's calculator Pascal, 1645
                 3 Product difference engine Babbage, 1822