Who came up with C1V1 = C2V2?
tl;dr It's so simple it was likely never published as a &quot;research result&quot;, since it stems quite directly from definitions.

It's a small step from the conservation of matter and the definition of concentration.
By definition: $C = \frac{n}{V}$, thus $n = CV$. If you dilute with pure solvent, you don't change the amount of solute that you have, in other words: $n_1 = n_2$. Using the previous equation, you get $C_1V_1 = C_2V_2$.