In 1885–1886 Toll took part in an expedition to the
New Siberian Islands, organized by the
St. Petersburg Academy of Sciences and led by
Alexander Bunge. Eduard Toll explored the
Great Lyakhovsky Island,
Bunge Land,
Faddeyevsky Island,
Kotelny Island, as well as the western shores of the
New Siberia Island. In 1886 Toll thought that he had seen an unknown land north of Kotelny. He guessed that this was the so-called "Zemlya Sannikova" (
Sannikov Land), a land that
Yakov Sannikov and
Matvei Gedenschtrom claimed to have seen during their 1808–1810 expedition, but whose existence had never been proved. Eduard Toll was among the first to report in detail about the abundance of Pleistocene fossils found within
Bolshoy Lyakhovsky Island, one of the New Siberian Islands. Under a peat composed of water mosses covering what he described as "perpetual ice", now known to be
permafrost, Toll found fragments of willow and the bones of post-
Neogene mammals, like the shoulder-bone of a
sabre-toothed tiger. He also reported having found in a frozen, sandy clay layer and lying on its side, a complete
Alnus fruticosa tree 15 to 20 ft (4.5 to 6 m) in length, including roots, with leaves and cones adhering. His reports have been frequently either misrepresented or badly garbled by popular accounts of his findings, stating it to be a plum tree of a different size. The academy appreciated the results of this expedition as "a true geographical deed". In 1893 Toll led an expedition of the Petersburg Academy of Sciences to the northern parts of
Yakutia and explored the region between the lower reaches of the
Lena and
Khatanga Rivers. He became the first to map the
plateau between the
Anabar and
Popigay Rivers and a mountain ridge between the
Olenek and Anabar Rivers (which he named after
Vasily Pronchischev). He also carried out geological surveys in the basins of the following rivers:
Yana,
Indigirka, and
Kolyma. In one year and two days the expedition covered 25,000 km, of which 4,200 km were up the rivers, carrying out geodesic surveys en route. Owing to the difficulties of the expedition and his hard work, the Russian Academy of Sciences awarded Toll the
N.M. Przhevalsky Large Silver Medal. In 1899 Toll took part in a voyage of the
icebreaker Yermak under the command of
Stepan Makarov to the shores of
Spitsbergen. ==Toll's last venture: the Russian Polar Expedition, 1900–1903==