grammar. The Sanskrit grammar of Pāṇini (c. 520 – 460 BCE) contains a particularly detailed description of Sanskrit morphology, phonology and roots, evincing a high level of linguistic insight and analysis. Ayurveda medicine traces its origins to the Vedas, Atharvaveda in particular, and is connected to Hindu religion. The Sushruta Samhita of Sushruta appeared during the 1st millennium BC. Ayurvedic practice was flourishing during the time of Buddha (around 520 BC), and in this period the Ayurvedic practitioners were commonly using Mercuric-sulphur combination based medicines. An important Ayurvedic practitioner of this period was Nagarjuna, accompanied by Surananda, Nagbodhi, Yashodhana, Nityanatha, Govinda, Anantdev, Vagbhatta etc. During the regime of Chandragupta Maurya (375-415 AD), Ayurveda was part of mainstream Indian medical techniques, and continued to be so until the Colonial period. The main authors of classical Indian mathematics (400 CE to 1200 CE) were scholars like Mahaviracharya, Aryabhata, Brahmagupta, and Bhaskara II. Indian mathematicians made early contributions to the study of the decimal number system, zero, negative numbers, arithmetic, and algebra. In addition, trigonometry, having evolved in the Hellenistic world and having been introduced into ancient India through the translation of Greek works, was further advanced in India, and, in particular, the modern definitions of sine and cosine were developed there. These mathematical concepts were transmitted to the Middle East, China, and Europe and led to further developments that now form the foundations of many areas of mathematics. China and the Far East The first recorded observations of solar eclipses and supernovae were made in China. On July 4, 1054, Chinese astronomers observed a guest star, a supernova, the remnant of which is now called the Crab Nebula. Korean contributions include similar records of meteor showers and eclipses, particularly from 1500-1750 in the Annals of the Joseon Dynasty. Traditional Chinese Medicine, acupuncture and herbal medicine were also practised, with similar medicine practised in Korea. Among the earliest inventions were the abacus, the public toilet, and the "shadow clock". Joseph Needham noted the "Four Great Inventions" of China as among some of the most important technological advances; these were the compass, gunpowder, papermaking, and printing, which were later known in Europe by the end of the Middle Ages. The Tang dynasty (AD 618 - 906) in particular was a time of great innovation. A good deal of exchange occurred between Western and Chinese discoveries up to the Qing dynasty. However, Needham and most