It is not widely known that the first correct proof of $E=mc^2$ was given by von Laue. Einstein never succeeded in giving complete and accurate proof. I came to know this when I was reading Hans Ohanion's book titled as "Einstein's Mistakes: The Human Failings of Genius".
Can anybody supply the PDF copy or web-link to this proof (in English)?
Well, I am sure Wikipedia has the answer but it is quicker to pull it from my bookmarks: I velieve this is what you want.
https://en.wikisource.org/wiki/Translation:On_the_Dynamics_of_the_Theory_of_Relativity
In passing, the tone of your question is poor: research is a collective endeavour and nobody, certainly not Einstein himself, has ever thought that he got all of special relativity and its consequences alone.
