El ruler. Ebony with Japanese lacquer (handle missing), c. 1820. The metric system was introduced troughout the kingdom by King William I in 1816. Measures like this el ruler were used to convert from old units into the new metric standard. Three units are shown on different sides: Amsterdam els, Batavian els, Rhineland feet. The fourth side shows the metric units in 'palms of one Dutch el'. One Dutch el was equal to one metre. In the royal decree of 1817 the new units, which had been developed in France, were given names based on the old Dutch systems of weights and measures. Calling the new units 'Dutch' served to differentiate the new from the old units.