Ain-i-Akbari in 1596-97 is book composed by Abul Fazl . This is part of a larger biographic work he wrote for king akabar ( 16th century India). A refernce to lonar is found in this book, a tranlation of which is quoted below from govt of Maharashtra gazette .
“‘Lonar is a division of Mehkar, and is a place of great sanctity. The Brahmans call it Bishan Gaya. There are three Gayas, where the performance of good works can be applied as a means of deliverance to the souls of deceased ancestors: namely Gaya in Bihar, which is dedicated to Brahma, Gaya near Bijapur, dedicated to Rudra, and this one. Here is also a reservoir, having a spring in it, of great depth, and measuring a kos in length and in breadth, and surrounded by lofty hills. The water is brackish, but when taken from the centre, or at its sides, it is sweet. It contains the essential materials for the manufacture of glass and soap, and saltpetre is here produced and yields a considerable revenue. On the summit of a hill is a spring at the mouth of which is carved the figure of a bull. The water never flows from this spring to the other, but when the thirtieth lunar day falls on a Monday its stream flows into the large reservoir. In the neighbourhood is a zamindar called Waila, of the Rajput tribe, commanding 200 horse and 2,000 foot. Another is called Sarkath, also a Rajput, and possesses 100 horse and 1,000 foot ‘.”