Picatrix Rubeus page 220:
“Those who intend to involve themselves in this science ought to know that it is by the works and experiments they do in this world that profound and secret sciences are known, and by works and experiments doubts are solved. This is because when anyone accomplishes his desires, his doubts are settled. You should indeed be greedy in all the things, and about all the things, that we have taught you so far, and you should be faithful in the operations themselves, and continually observe the ways of the sages and the habits of the ancients in the operations of this science.”
Though Picatrix says earlier that we should have faith in magic and not trifle with it in order to prove whether it exists to ourselves, the author urges students of magic to test individual techniques out in order to verify them. And do it as much as is possible. As he says, be greedy.
And now I’m done for the time being.