Precession of Mercury's longitude of perihelion - (so called "anomaly")

The calculation of the advance of perihelion using Newtonian Celestial Mechanics was
carried out by Urbain L Verrier (1811-1877), with 43 arc seconds per century unaccounted
for.
Urbain Le Verrier is best known for the calculations which led to the discovery of Neptune.

Uranus was discovered by Sir William Herschel on 13 March 1781 (4 years after Le Verrier died).

The so-called "anomaly" that the prominent Albert Einstein "corrected" with his
Wonderful Theory of General Lies and Crackpottery was Le Verrier not having a
telescope quite as good as Herschel's and nothing to do with his calculations, he
simply hadn't included Uranus because he didn't know about it.