As the radius of the two missionaries' work expanded, plans for Christian missionary outposts in the area began to develop. During his time in Africa, Rebmann kept a diary from 1848 until the end of his life. In the diary, Rebmann writes of the way his trust in his Christianity kept him stable in the continent of Africa, where only very few Europeans had ventured before him. An extract from the diary, which Rebmann in turn took from the Bible (Psalm: 51, 12) reflects Rebmann's belief in his faith: "Restore to me joy of your salvation and grant me a willing spirit, to sustain me." In 1848, Rebmann was the first European to see Mount Kilimanjaro. The following year, he saw Mount Kenya together with his colleague Krapf. On the October 16, 1847, the two men set out for the interior of Kenya. With them came eight tribesmen and a local caravan leader named Bwana Kheri. This expedition was designed with the goal of establishing some of the first mission posts in the region. The journey was successful, and the group of tribesmen and the missionaries returned to Mombasa on October 27. Sometime during their journey or their stay in the region, Rebmann and Krapf learned of a great mountain referred to as 'Kilimansharo', which reached the clouds and which was 'capped in silver'. The two men, like most Europeans at the time, were under the impression that snow and ice could not exist so close to the equator, and failed to realize the significance of the mountain being 'topped with silver'. However, the two missionaries, who had become just as much explorers as they were missionaries, became quite interested in Kilimanjaro, and Krapf sought permission of the Mombasa governor for an expedition to the land of the Jagga, a people now known as the Chaga, who lived and live on the actual slopes of Kilimanjaro. Krapf told the governor that this journey would be work-based. Despite this, Krapf actually did not accompany Rebmann on the journey, so only Bwana Kheri and Rebmann left for Kilimanjaro on April 27, 1848. Within two weeks, Rebmann and his guide were within sight of the mountain. He noted in his journal the strange white on the summit of Kilimanjaro, and he questioned his guide on what he thought it was. According to Rebmann's log, the guide 'did not know what it was, but supposed it was coldness'.