I recall in some of his Lecture's Terence tried similar things, I apologize I don't have any links or transcripts and a google search didn't turn up much.

Rather than trying to have entities corroborate a number or something like that, he would ask the mushroom to "tell me something I couldn't possible know". If he could get the experience to give him this kind of novel information that would in some ways validate the "reality" of the experience. He never had much luck with it as I recall.

I am intrigued by the handful of people on the nexus who have reported smoking DMT and encountering various Hindu dieties, of which they had no prior knowledge, and then coming and back and finding out their experiences gave them accurate depictions of these dieties down to the finest details. There are only a few, and again I don't have any links offhand, but they are pretty interesting reports.