The "Medicinisch-Demographische Expedition" of 1913/1914 was undertaken by physicians like Alfred Leber (1881–1954) and Ludwig Külz (1875–1938), but also included the German painter Emil Nolde (1867–1956). The expedition travelled overland from Berlin through Russia and Asia. This map shows all stations of this expedition (click on the map for a larger view).
Map of the medical-demographic expedition to German New Guinea, map, 2013, creator: Maximilian Dörrbecker (Chumwa); source: Wikimedia Commons, https://commons.wikimedia.org/wiki/File:Karte_zur_Medizinisch-demographischen_Deutsch-Neuguinea-Expedition.jpg, , https://creativecommons.org/licenses/by/2.5/.