Three missionaries, confined to the coastal belt, heard of the region of Unyamwezi in the northwest of what is now Tanzania and exaggerated its size to include a large part of the continental interior.

[1] Bantu peoples moved into the region between the Great Lakes and the Indian Ocean some time after 1000 BC and mingled with the local population.

Slaves brought from the Congo Basin or the Great Lakes region would be held at Tabora, then sent down to the coast in small groups for onward shipment.

[11] Early in 1844 Sultan Sayyid Said gave the German missionary Johann Ludwig Krapf (1810–1881) permission to establish a mission on the coast.

[14] On 10 June 1849 Jakob Erhardt (1823–1901) and John Wagner arrived at the Rabbai Mpia mission station near Mombasa.

"[19] In 1850 Krapf exclaimed that, "Had we sufficient pecuniary means at our command, and were it not our bounden duty to subordinate all secondary objects to our chief vocation, which consists in the preaching of the Gospel, the map of East Africa would soon wear another aspect.

"[20] Later that year the Church missionary intelligencer published an account by Krapf of a journey to Ukambani[b] that he had made in November and December 1849.

He speculated that the Niger and its tributary the Tshadda (Benue), the Congo, Nile and Kilimani (Quelimane – near to the mouth of the Zambezi) would all provide access to the center of Africa.

[24] According to Rebmann, whose account was published in Krapf's memoirs, They represented to him that the Sea of Uniamesi was simply a continuation of the Lake Niassa, the latter, according to them, striking out westward from its northerly direction, and then spreading itself out even to a greater expanse than hitherto, so as to approach the mountains which pass through the centre of the continent, and form a most important and impenetrable barrier and water-shed.

The northern side of this barrier contains the sources of the Nile, of Lake Tsad, and of the river Chadda, while the south side sends its waters partly to the Atlantic Ocean, by the river Congo or Zaire, partly to the Indian Ocean by the Jub, Dana and Osi, and also, as I think highly probable, to the great lake of the interior itself.

[27] August Heinrich Petermann published the map in his Mittheilungen, but warned that the missionaries may not have accounted sufficiently for exaggeration by their informants.

He said, "The existence of this sea was certified to me during my stay at Khartoum by a pilgrim from Mecca, who inhabits Central Africa, and who gave Mahmoud Pasha, one of the Viceroy's ministers, particulars corresponding to Mr. Rehman's map.

[35] Burton met king Kimweri ye Nyumbai, once a powerful warrior who had controlled the trade routes to the interior but now extremely old.

[37] At Kazeh Burton and Speke found a mixed population of Nyamwezi, Tutsi and Arabs engaged in cattle farming and cultivation of foods such as rice, cassava, pawpaw and citrus.

[38] The land sloped down from there to Lake Takanyika [sic], or Uniamesi, which they reached on 3 March 1849 and where they recorded an elevation of 1,843 feet (562 m).

[37][d] Burton and Speke found that the lake extended about 300 miles (480 km) north from Ujiji, where it was closed by a crescent-shaped mountain range.

Speke recorded an elevation of 3,788 feet (1,155 m)[e] and was told that a river left the north of the lake and flowed into the Nile.

Speke made a long journey with James Augustus Grant between October 1860 and February 1863, traveling from the coast opposite Zanzibar via Tabora and Uganda to Khartoum.

[41] In 1866–73 David Livingstone left the coast at Pemba, followed the Ruvuma River inland and walked to the southern end of Lake Nyasa, which he rounded to the west.