Even digital spanners have been made which use sheets or feelers to set the size, some types uses a serrated edge to lock the moveable jaw to size.
There is also a class of adjustable that automatically adjusts to the nut size.
The adjustable spanner was invented by Edwin Beard Budding (1795-1846), who also invented the lawnmower.
A later form of adjustable was invented in Sweden by J. P Johansson in 1892.
Ref 1: " class="external">http://www.bbc.co.uk/history/historic_figures/budding_edwin_beard.shtml More information on adjustable spanners can be found at: http://www.adjustable.archivist.info