In 1663, after a long stay in London, Vansleb planned a journey to Ethiopia in search of religious manuscripts for his patron Ernest I, Duke of Saxe-Gotha.
Beginning his travels from Marseille on 20 May 1671, Vansleb felt sick on arrival in Cyprus (which he explained as caused by the plague then scouring the island).
Despite being very sick for an extended time (and preparing to leave this world, as he explains) he managed to visit Tripoli, Damascus, Aleppo and Seyda during the next 10 months, finally arriving in Damietta, Egypt, in March 1672.
Instead he relates a report from two Capuchin missionary brothers, P. Protais and Charles-François d'Orléans, who had visited all the main sites of Upper Egypt in 1668.
Vansleb is a keen observer, repeatedly trying to get to the bottom of things, yet at other times accepting obscure and spurious explanations without much resistance, for example on the mating rituals of the Nile crocodile.