Price of Gold since 1791 in constant 2012 USD:
Click on chart to open
And a data set for gold prices since 1257: http://measuringworth.com/gold/#
You can't really make a data set for any fiat currency since 1257, cause none really exist anymore... though you can make sets of numismatic values of some. So risk-adjusted value of gold is X>0 over any time horizon. Risk-adjusted value of any fiat currency over much of the historical time horizon is X~0. That is, of course, if unlike Keynes you do believe that the long-run matters...