The Northeast Passage (abbreviated as NEP) is, from the European and northern Atlantic point of view, the shipping route to the Pacific Ocean, along the Arctic coasts of Norway and Russia. The western route through the islands of Canada is accordingly called the Northwest Passage (NWP). The NEP traverses (from west to east) the Barents Sea, Kara Sea, Laptev Sea, East Siberian Sea, and Chukchi Sea, and it includes the Northern Sea Route (NSR). The Northern Sea Route is a portion of the NEP; it is defined in Russian law and does not include the Barents sea and therefore does not reach the Atlantic Ocean. However, since the NSR has a significant overlap over the majority of the NEP, sometimes the NSR term has been used to refer to the entirety of the Northeast Passage. The Northeast Passage is one of several Arctic maritime routes, the others being the Northwest Passage (going through the Canadian Arctic Archipelago and the coast of Alaska) and the Transpolar Route (going through the North Pole). The first confirmed complete passage, from west to east, was made by the Swedish Finnish explorer Adolf Erik Nordenskiöld, with the Swedish ship Vega 1878–79 backed by the royal funding of king Oscar II of Sweden. Nordenskiöld was forced to winter just a few days' sailing distance from Bering Strait, due to pack ice. The motivation to navigate the Northeast passage was initially economic. In Russia, the idea of a possible seaway connecting the Atlantic and the Pacific Oceans was first proposed by the diplomat Gerasimov in 1525. However, Russian settlers and traders on the coast of the White Sea, the Pomors, had been exploring parts of the route as early as the 11th century. During a sail across the Barents Sea in search of the Northeast Passage in 1553, English explorer Hugh Willoughby thought he saw islands to the north, and islands called Willoughby's Land were shown on maps published by Plancius and Mercator in the 1590s, and they continued to appear on maps by Jan Janssonius and Willem Blaeu into the 1640s. By the 17th century, traders had established a continuous sea route from Arkhangelsk to the Yamal Peninsula, where they portaged to the Gulf of Ob. This route, known as the Mangazeya seaway, after its eastern terminus, the trade depot of Mangazeya, was an early precursor to the Northern Sea Route. East of the Yamal, the route north of the Taimyr Peninsula proved impossible or impractical. East of the Taimyr, from the 1630s, Russians began to sail the Arctic coast from the mouth of the Lena River to a point beyond the mouth of the Kolyma River. Both Vitus Bering (in 1728) and James Cook (in 1778) entered the Bering Strait from the south and sailed some distance northwest, but from 1648 (Semyon Dezhnev) to 1879 (Adolf Erik Nordenskiöld) no one is recorded as having sailed eastward between the Kolyma and Bering Strait.