Explanation:

Abu Rayhan Beruni or Alberonius (Latin) was a Persian Scholar and polymath of the 11th century. He accompanied Mahmud in his conquests to South Asia.
A 77 kilometer impact crater in moon is named after him : Al-Beruni Crater
Al Beruni, though travelled with Mahmud, but his successor Masud was his real patron.
Apart from his writing languages Arabic and Persian, he knew Sanskrit and Greek. Al Beruni’s 146 works are on Astronomy (35 books (maximum)), Astrology, Chronology, Time Measurement, Geography, cartography, Mathematics, Mechanics, Medicine, Pharmacology, Gems, India, Literature etc.
 It’s worth note that about India, he did not write much on battles and wars. He wrote on contemporary culture, traditions and customs. His book Ta?qiq ma l’l-Hind (“al-Biruni’s India”) is also called “Indica” and is a work related to Indian Philosophy and religion.
The other book Kitab al-Qanun al-Mas’udi (Mas’udi Canon) is about Astronomy, Geography and Engineering, named after Mas’ud, son of Mahmud of Ghazni, to whom he dedicated. Using astrolabe, he first calculated the height of the mountain by going to two points at sea level with a known distance apart and then measuring the angle between the plain and the top of the mountain for both points.