The following systems arose from earlier systems, and in many cases utilise parts of much older systems. For the most part they were used to varying degrees in the Middle Ages and surrounding time periods. Some of these systems found their way into later systems, such as the Imperial system and even SI. English system Before Roman units were reintroduced in 1066 by William the Conqueror, there was an Anglo-Saxon (Germanic) system of measure, of which few details survive. It probably included the following units of length: fingerbreadth or digit inch ell or cubit foot perch, used variously to measure length or area acre and acre's breadth furlong mile The best-attested of these is the perch, which varied in length from 10 to 25 feet, with the most common value (16 feet or 5.03 m) remaining in use until the twentieth century. Later development of the English system continued in 1215 in the Magna Carta. Standards were renewed in 1496, 1588 and 1758. Some of these units would go on to be used in later Imperial units and in the US system, which are based on the English system from the 1700s. Danish system From May 1, 1683, King Christian V of Denmark introduced an office to oversee weights and measures, a justervæsen, to be led by Ole Rømer. The definition of the alen was set to 2 Rhine feet. Rømer later discovered that differing standards for the Rhine foot existed, and in 1698 an iron Copenhagen standard was made. A pendulum definition for the foot was first suggested by Rømer, introduced in 1820, and changed in 1835. The metric system was introduced in 1907. Length skrupel – Scruple, linie linie – Line, tomme tomme – Inch, fod palme – Palm, for circumference, 8.86 cm kvarter – Quarter, alen fod – Defined as a Rheinfuss 31.407 cm from 1683, before that 31.41 cm with variations. alen – Forearm, 2 fod mil – Danish mile. Towards the end of the 17th century, Ole Rømer connected the mile to the circumference of the earth, and defined it as 12000 alen. This definition was adopted in 1816 as the Prussian Meile. The coordinated definition from 1835 was 7.532 km. Earlier, there were many variants, the most commonplace the Sjællandsk miil of 17600 fod or 11.130 km. Volume potte – Pot, from 1603 foot3 smørtønde – Barrel of butter, defined as 136 potter from