Editing Mohenjo-daro (section)

=== The Mohenjo-daro ruler ===
{{anchor|Ruler}}
The Indus Valley civilisation employed [[ruler]]s made of [[ivory]] for measuring length circa 1500&nbsp;BCE.<ref name="Whitelaw14"/> The Mohenjo-Daro ruler is divided into units corresponding to {{convert|1.32|inch|mm|order=flip}} and these are further marked in decimal subdivisions with great accuracy, to within {{convert|0.005|in|mm|order=flip|abbr=on}}. A ruler found at [[Lothal]] (2400&nbsp;BCE) is calibrated to about {{convert|1/16|inch|mm|order=flip|abbr=on}}.<ref name="Whitelaw14">Whitelaw, p. 14.</ref> The decimal subdivision on the ruler is noteworthy, as it predates the modern metric system by 3000 years or more. The base unit used was known as the ''angula'' (finger) and is about 17&nbsp;mm. A piece of shell found in Mackay's excavation is very precisely incised with lines spaced {{convert|0.264|inch|mm|order=flip|abbr=on}} apart. Ancient bricks found throughout the region have dimensions that correspond to these units.<ref>Whitelaw, p. 15.</ref>