Hey guys! I have read online (...)
that's the internet for you....
the first person to give a value for Avogadros number wasn't good old Lorenzo Romano Amedeo Carlo Avogadro di Quaregna e di Cerreto - he didn't even have the faintest idea about it, though it is named in his honor.
the same is true for Prout, esp. when he published his theory in 1815
hence, he possibly couldn't have made use of it: it wasn't known before long after Prout's death in 1850
it took 'till 1865 that J.J. Loschmidt at least did measure the ballpark of named number correctly