https://www.youtube.com/watch?v=eBfKC3h4VQUInteresting little film from Matt Rogers recounting some very early Px researchers predating Percival Lowell, such as:

William Herschel, Germany & Britain, 18th Century - found Uranus with its tilted orbit, causing other European astronomers to begin searching for Px

Alexis Bouvard, "The Godfather of Px Research," Early 19th Century France

Urbain Le Verrier, 19th Century French mathematician who pinned down the coordinates of Neptune and then predicted the existence of Px mathematically.

John Couch Adams, 19th Century British mathematician who also used mathematics to locate Neptune and then extrapolated Px.

Johann Gottfried Galle, 19th Century German astronomer who used these mathematical coordinates to visually locate Neptune by telescope