<p>Seiken,</p>
<p>The proof used no calculus so quite obviously it had a vague assumption (ie. momentum = E/c for photon). It was not the greatest proof, but still good enough to be published in my school magazine. And more than that, through this attempt I learned many stuffs (like conservation of linear momentum) prior to my class mates. 
You can find a similar proof here: [E</a> = mc2](<a href=“http://www.drphysics.com/syllabus/energy/energy.html]E”>E = mc2)</p>
<p>BTW, what chances do I make at HMC?</p>
<p>PS:
I loved this from the web page of Harvey Mudd,</p>
<p>We dare professors to give us problems that they think we can’t solve. Then we stay up all night just to prove them wrong (and also because, secretly, we enjoy it).</p>