In 1633–38 Ilya Perfilyev and Ivan Rebrov sailed down the Lena and east along the Arctic coast to the mouth of the Yana and reached the Indigirka estuary. In 1636–42 Elisei Buza followed essentially the same route. In 1638–40, Poznik Ivanov ascended a tributary of the lower Lena, crossed the Verkhoyansk Range to the upper Yana and then crossed the Chersky Range to the Indigirka.[5]