The Mysterious Prosperous Tang_Dynasty, Chapter 422: A lone goose comes from the sea, not daring to look at the moat.
Finding the African continent was not such a rare event. During the Tang Dynasty, merchants already had records of sailing and reaching the Somali region in Africa. It just required several more transits between Tianzhu (ancient India) and Dashi (the Abbasid Caliphate). For instance, there are clear records showing that it took about 90 days to travel from Guangzhou to Basra (Pashi La), and only 30 days to reach the three countries in East Africa.