Einstein paper

Have you ever wanted to read how Einstein presented the concept of E equals M C squared?

It's only a 3 page paper, and the line of thought seems inspired by what is going on with what we now call radiation and what is happening when an object gives off energy as radiation.

we are led to the more general conclusion that the mass of a body is a measure of its energy-content;

In the paper he lays out a test of this hypothesis - by measuring the mass of radium salts over time.