Editing Odometer (section)

==== Han dynasty and Three Kingdoms period ====
The odometer was also independently invented in [[History of Science and Technology in China|ancient China]],{{sfn | Needham | 1965 | pp=280–286}} possibly by the prolific inventor and early scientist [[Zhang Heng]] (78 AD – 139 AD) of the [[Han dynasty]]. By the 3rd century (during the [[Three Kingdoms]] Period), the Chinese had termed the device as the 'jì lĭ gŭ chē' (記里鼓車), or '[[li (unit)|li]]-recording drum carriage' (Note: the modern measurement of li = {{Cvt|1640|ft|order=flip}}).{{sfn | Needham | 1965 | p=281}} Chinese texts of the 3rd century tell of the mechanical carriage's functions, and as one li is traversed, a mechanical-driven wooden figure strikes a drum, and when ten li is traversed, another wooden figure would strike a gong or a bell with its mechanical-operated arm.{{sfn | Needham | 1965 | p=281}}

Despite its association with Zhang Heng or even the later [[Ma Jun (mechanical engineer)|Ma Jun]] (c. 200–265), there is evidence to suggest that the invention of the odometer was a gradual process in Han dynasty China that centered around the ''huang men'' court people (i.e. eunuchs, palace officials, attendants and familiars, actors, acrobats, etc.) that would follow the musical procession of the royal 'drum-chariot'.{{sfn | Needham | 1965 | p=283}} The historian [[Joseph Needham]] asserts that it is no surprise this social group would have been responsible for such a device, since there is already other evidence of their craftsmanship with mechanical toys to delight the emperor and the court. There is speculation that some time in the 1st century BC (during the Western Han dynasty), the beating of drums and gongs were mechanically-driven by working automatically off the rotation of the road-wheels.{{sfn | Needham | 1965 | p=283}} This might have actually been the design of one [[Luoxia Hong]] ({{circa|110&nbsp;BC}}), yet by 125 AD the mechanical odometer carriage in China was already known (depicted in a mural of the [[Xiaotang Mountain Han Shrine|Xiaotangshan Tomb]]).{{sfn | Needham | 1965 | p=283}}

The odometer was used also in subsequent periods of Chinese history. In the historical text of the ''[[Book of Jin|Jin Shu]]'' (635 AD), the oldest part of the compiled text, the book known as the ''Cui Bao'' ({{circa|300&nbsp;AD}}), recorded the use of the odometer, providing description (attributing it to the Western Han era, from 202 BC–9 AD).{{sfn | Needham | 1965 | p=282}} The passage in the ''Jin Shu'' expanded upon this, explaining that it took a similar form to the mechanical device of the [[south-pointing chariot]] invented by [[Ma Jun (mechanical engineer)|Ma Jun]] (200–265, see also [[differential (mechanical device)|differential]] gear). As recorded in the ''[[History of Song (Yuan dynasty)|Song Shi]]'' of the [[Song dynasty]] (960–1279 AD), the odometer and south-pointing chariot were combined into one wheeled device by engineers of the 9th century, 11th century, and 12th century. The ''[[Sunzi Suanjing]]'' (Master Sun's Mathematical Manual), dated from the 3rd century to 5th century, presented a mathematical problem for students involving the odometer. It involved a given distance between two cities, the small distance needed for one rotation of the carriage's wheel, and the posed question of how many rotations the wheels would have in all if the carriage was to travel between point A and B.{{sfn | Needham | 1965 | p=282}}