Someone published a simple computation of the relativistic shift in Mercury's perihelion (over and above classical, ie. the small correction over the classical-mechanical shift) by more or less using the principle of relativity. I believe it was a she and she computed how far mercury travels in the time it takes for a photon to reach Mercury from the Sun. I'm not sure what value she got but it was probably very close - like within 5 or 10% of a full General-relativistic or Goldstein-mechanics book approach. Another guy did it by calculating the difference in the acceleration of Mercury due to GR effects and proceeding from there. He gets like 36.7 arcseconds. Just wondering, does anyone know where that calculation by the woman is? I like their off-the-cuff estimates as there is some good physics in those approaches. I just lost the article - I will eventually find it so no big worry. Thank you.