copper, bronze, and ceramics. One excavated pan balance from Mohenjo-daro (2600–1900 BCE) was constructed using a cord-pivot type fulcrum, a bronze beam, and two pans. A number of excavated surveying instruments and measuring rods have yielded evidence of early cartographic activity. Weights and measures are mentioned throughout the religious and secular works of the Vedic period in India. Some sources that mention various units of measurement are Satapatha Brahmana, Apastamba Sutra, and the Eight Chapters of the grammarian Pāṇini. Indian astronomers kept a pañchānga for calculations of tithi (lunar day), vāra (weekday), naksatra (asterism), and karan (half lunar day) for social and religious events. Klostermaier (2003) states that: "Indian astronomers calculated the duration of one kalpa (a cycle of the universe during which all the heavenly bodies return to their original positions) to be 4,320,000,000 years." According to epigraphic evidence, we have references of measurement units such as – “Kulyavapa”, “dronavapa”, “adhavapa” and “Pataka” from Bengal, nivratana” and “bhumi” from Central India and “nivartana from Western India. Post Maha Janapadas period—High Middle Ages (400 BCE–1200 CE) Steelyard balances—found in India since the 4th century BCE—have been excavated from the archaeological sites of Gandhara and Amravati. Evidence of a complex system of weights and measures existing in use for multiple purposes under the central control of the Maurya administration (322–185 BCE) is found in the Arthashastra. Archaeologist Frank Raymond Allchin outlines the details of the measurement systems of the Maurya state: Depiction of equal arm balances is found in the art of Ajanta cave (No. 17) in the Maharashtra state. Beams of steelyard balances have been unearthed from the 8th century CE archaeological sites at Sirpur and Arang. The research conducted by Abū Rayḥān Muḥammad ibn Aḥmad al-Bīrūn, an Islamic scholar who undertook one of the first studies of India's traditions in his Tahriq-e-Hind, also reflect on the regular usage of the steelyard in India. Late Middle Ages—Republic of India (1200 CE–1947 CE onwards) The Chinese merchant Ma Huan (1413–51) outlines the standardised weight and currency system in place at the port city of Cochin. Ma Huan noted that gold coins, known as fanam, or locally known as "panam", were issued in Cochin and weighed a total of one fen and one li according to the Chinese standards. They were of fine quality and could be exchanged in China for 15 silver coins of four-li weight each. The Mughal empire (1526–1857)