Columbus believed that by sailing west, he could reach the east coast of Asia. He highlighted passages from Marco Polo's work, such as those describing Japan as "Zipangu" and emphasizing its wealth, spices, and precious stones. Columbus was inspired by Polo's tales and determined to find this path that Polo believed would make him an extremely wealthy king.
Moreover, there were other significant books and navigational works that influenced Columbus' thinking and preparations, including maps such as the Ptolemy's Geographia that depicted an Asian landmass much closer to Europe than it actually was. It is important to remember that Columbus lived before precise cartographic techniques and measurements of Earth's size and proportions had been refined, further driving his miscalculation that a relatively short eastward sail from Europe would eventually reach Asia.