Percival Lowell was an American businessman, author, mathematician, and astronomer who fueled speculation that there were canals on Mars, and furthered theories of a ninth planet within the Solar System. He founded the Lowell Observatory in Flagstaff, Arizona, and formed the beginning of the effort that led to the discovery of Pluto 14 years after his death.
Percival Lowell in 1904
Lowell (front row, rightmost) in Joseon, before the departure of the first Korean mission to the United States
Martian canals depicted by Percival Lowell
Percival Lowell in 1914, observing Venus in the daytime with the 24-inch (61 cm) Alvan Clark & Sons refracting telescope at Flagstaff, Arizona
During the late 19th and early 20th centuries, it was erroneously believed that there were "canals" on the planet Mars. These were a network of long straight lines in the equatorial regions from 60° north to 60° south latitude on Mars, observed by astronomers using early telescopes without photography.
This is a modern ground-based telescope picture of Mars which uses lucky imaging to achieve a near perfect theoretical resolution. However, due to astronomical seeing, it is extremely difficult to see finer details.
Martian canals depicted by Percival Lowell