In a web-site in English titled "Perihelion Precession of the Planets", there is a table on observed rates from Mercury (5.75 seconds/year) to Neptune (0.36 seconds/year). In these, direction of precession is the direction of planet's revolution, and these magnitude are assumed to be constant. Let's assume this table is true. So, this phenomenon will be caused by two bodies: planet each and Sun.
Adams and Le Verrier predicted the existence of Neptune and its position on the celestial sphere (from the precession of Uranus's position). But it was temporary and exceptional precession (perturbation).
