text: what is the origin of the folding rule?   2000 years of world history  the "historical folding rule" visualizes history on two different levels.  the event side on the event side, each centimeter represents ten years of world history. it recalls significant data from the roman times until the millenium, from jesus christ to the internet.  the periods side  the periods side presents world history divided into its fundamental periods. entries on intellect, powers, and the arts on a backdrop ranging from late antiquity until the modern times provide a context for individual events.  other than conventional history books the "historical folding rule" elucidates historical correlations in an extraordinary way: it provides a synthesis of clarity, keen intellect and wit.