Before the age of exploration, a good number European scholars speculated about the Atlantic beyond the Iberian peninsula, whether it was the location of Atlantis, or whether or not Japan could be reached by sailing west. Was there any analogous discussion in China and/or Japan about what lay across the Pacific Ocean?
Xu Fu, the most famous explorer in Asia to answer this question, DID have some voyages in the Pacific, but for a strange reason, and some superstitions, too!
In 219 BC, Xu Fu was sent with three thousand virgin boys and girls to retrieve the elixir of life from the immortals on the Mount Penglai, including Anqi Sheng, who was purportedly a magician who was already a thousand years old. Xu sailed for several years without finding the mountain. In 210 BC, when Qin Shi Huang questioned him, Xu Fu claimed there was a giant sea creature blocking the path, and asked for archers to kill the creature. Qin Shi Huang agreed, and sent archers to kill a giant fish. Xu then set sail again, but he never returned from this trip. The Records of the Grand Historian says he came to a place with "flat plains and wide swamps" (平原廣澤) and proclaimed himself king, never to return.