In ancient times the traders crossed over the Himalayan watershed from Tibet over the Tukung â€“ la pass. Descending down the head waters of the Tawang Chhu River, they crossed the Sela ridge along a yak trail, with their caravans of wool, skins, precious stones and yak butter to reach the barter markets in Assam. Here they exchanged their loads for salt, tea, cloth, and other commodities. This route was first explored by British surveyors lead by F.M. Bailey in 1913 â€“ and came to be called â€˜The Bailey Trailâ€™.