The Indian Astronomer V. B. Ketkar (1853-1930) predicted TWO trans Neptune planets in 1911 in a letter to Bulletin of Astronomical Society of France in May 1911, page 277. Laplace Laws of satellites of Jupiter were modified and applied by Ketkar for arriving at this results.
The first planet (Brahma) discussed there is subsequently discovered as Pluto. The second planet (Vishnu) has not yet been discovered, and is currently referred to as "Planet X" by Astronomers.
Can one calculate the current location and observe it?