In the 1870s, the destination of the Tsangpo River (sometimes spelled "Sanpo") was unknown. Some hypothesized that it was the same river that flowed into the Bay of Bengal under the name of Brahmaputra (also known as "Dihang")? To solve this mystery, the colonial government of India sent a pundit explorer, known only as "G. M. N." to follow the Tsangpo and determine its ultimate destination. G. M. N. was accompanied by his assistant, a Sikkimese lepcha named Kinthup. After surveying a good portion of the river, the pair returned to India. In 1880, a Chinese Lama was employed to continue G. M. N.'s work, and Kinthup was again hired to accompany him. However, in May 1881, this Lama sold Kinthup as a slave to another Tibetan lama. All of Kinthup's surveying equipment and notebooks were taken from him, and he served as a slave until March 1882, when Kinthup finally managed to escape. He traveled east along the Tsangpo, and sought sanctuary in a Buddhist monastery, where he was welcomed by the head lama.
Despite this Kinthup carried out his surveying. Over the course of two and a half years, under the guise of religious pilgrimages, he made several long trips, surveying the extent of the Tsangpo and surrounding region, determining that the two rivers were indeed one and the same. Finally, in November 1884, he was able to return to India. It was not until 2 years later that his account was even recorded, and even then, his extraordinary accounts were doubted by some geographers. It was only more than 30 years later, when a proper survey was carried out, was his story confirmed.