Editing Water clock (section)

===India ===
{{main|Hindu units of time}}
N. Narahari Achar and [[Subhash Kak]] suggest that water clocks were used in [[History of India|ancient India]] as early as the 2nd millennium BC, based on their appearance in the ''[[Atharvaveda]]'.<ref>{{cite journal| url = http://www.ejvs.laurasianacademy.com/ejvs0402/ejvs0402.txt| title = On the meaning of AV XIX. 53.3: Measurement of Time?| access-date = 2007-05-11| last = Achar| first = N. Narahari| date = December 1998| journal = Electronic Journal of Vedic Studies| archive-date = 2015-09-23| archive-url = https://web.archive.org/web/20150923234634/http://www.ejvs.laurasianacademy.com/ejvs0402/ejvs0402.txt| url-status = dead}}</ref><ref>{{cite book |last=Kak |first=Subhash |author-link=Subhash Kak |date=2003-02-17 |chapter=Babylonian and Indian Astronomy: Early Connections |title=History of Science, Philosophy & Culture in Indian Civilization |volume=1 Part 4 |editor-last=Pande |editor-first=G. C. |pages=847–869 |arxiv=physics/0301078 |bibcode=2003physics...1078K}}</ref>''
According to N. Kameswara Rao, pots excavated from the [[Indus Valley Civilisation]] site of [[Mohenjo-daro]] may have been used as water clocks. They are tapered at the bottom, have a hole on the side, and are similar to the utensil used to perform ''[[abhiṣeka]]'' (ritual water pouring) on [[lingam]]s.<ref>{{cite journal | first = N. Kameswara | last = Rao |date=December 2005 | title = Aspects of prehistoric astronomy in India | journal = Bulletin of the Astronomical Society of India | volume = 33 | issue = 4 | pages = 499–511 | url = http://www.ncra.tifr.res.in/~basi/05December/3305499-511.pdf | access-date =2007-05-11 | quote =It appears that two artifacts from Mohenjo-daro and Harappa might correspond to these two instruments. Joshi and Parpola (1987) lists a few pots tapered at the bottom and having a hole on the side from the excavations at Mohenjadaro (Figure 3). A pot with a small hole to drain the water is very similar to clepsydras described by Ohashi to measure the time (similar to the utensil used over the lingum in Shiva temple for abhishekam). |bibcode = 2005BASI...33..499R }}</ref>

The [[Jyotisha]], one of the six [[Vedanga]] disciplines, describes water clocks called ''ghati'' or ''kapala'' that measure time in units of ''nadika'' (around 24 minutes). A clepsydra in the form of a floating and sinking copper vessel is mentioned in the ''[[Sürya Siddhānta]]'' (5th century AD).<ref>"A copper vessel (in the shape of the lower half of the water jar) which has a small hole in its bottom and being placed upon clean water in a basin sinks exactly 60 times in a day and at night." – Chapter 13, verse 23 of the ''Sürya Siddhānta''.</ref> At [[Nalanda mahavihara]], an [[Ancient higher-learning institutions|ancient Buddhist university]], four-hour intervals were measured by a water clock, which consisted of a similar copper bowl holding two large floats in a larger bowl filled with water. The bowl was filled with water from a small hole at its bottom; it sank when filled and was marked by the beating of a drum in the daytime. The amount of water added varied with the seasons, and students at the university operated the clock.<ref>{{cite book | last = Scharfe | first = Hartmut | title = Education in Ancient India | url = https://archive.org/details/educationancient00scha | url-access = limited | year = 2002 | publisher = Brill Academic Publishers | location = Leiden | isbn = 90-04-12556-6 | page = [https://archive.org/details/educationancient00scha/page/n177 171]}}</ref>

Descriptions of similar water clocks are also given in the ''[[Pancha-Siddhantika|Pañca Siddhāntikā]]'' by the polymath [[Varāhamihira]] in the 6th century, which adds further detail to the account given in the ''Sūrya Siddhānta''.{{Full citation needed|date=July 2019}} Further descriptions are recorded in the ''[[Brāhmasphuṭasiddhānta]]'' by the mathematician [[Brahmagupta]] in the 7th century. A detailed description with measurements is also recorded by the astronomer [[Lalla]] in the 8th century, who describes the ''ghati'' as a hemispherical copper vessel with a hole that is fully filled after one ''nadika''.<ref>"A copper vessel weighing 10 palas, 6 angulas in height and twice as much in breadth at the mouth—this vessel of the capacity of 60 palas of water and hemispherical in form is called a ghati." This copper vessel, which was bored with a needle and made of 3 1/8 masas of gold and 4 angulas long, gets filled in one nadika."{{Full citation needed|date=July 2019}}</ref>