Forma Negativa: Cannot we x Can we not

No similar topic on the forum. This one inquires as to the negative interrogative form of can. My grammar manual¹ gives the long form cannot as a one and indivisible (or solid) word mainly in negative interrogative questions, meaning we cannot--or perhaps should not--sandwich a pronoun between the can and the not.

"Cannot man, through scientific investigation, penetrate some of the secrets of nature?"
"Can man not...?" (BrE says no, you can't have man sandwiched in.)

Do you know of a grammar website that says yes, you can sandwich it or no, you cannot? Better yet, what does your grammar book say about it? Thank you.

-------------------------------
¹ Practical English Usage, by Michael Swan, 3rd Edition, p. 97, point # 121, item h.