Astronomer John Flamsteed observed a celestial object that he cataloged as 34 Tauri, but many years later William Herschel and other astronomers figured out Flamsteed saw a planet. Which one?

Astronomer John Flamsteed observed a celestial object that he cataloged as 34 Tauri, but many years later William Herschel and other astronomers figured out Flamsteed saw a planet. Which one?