Anything in the Constitution for "unhinged"?

[samintx]

President transmits to the President pro tempore of the Senate and the Speaker of the House of Representatives his written declaration that he is unable to discharge the powers and duties of his office

Trumpster can write (I think but he can't spell) but the Trumpster would never send that note to Congress. We know he is unfit but he doesn't know that fact.

I'm looking at my pocket Constitution but don't see the 21st Amendment application to the question.

PS: sorry I'm a little dull today….I get the 21st Amd now.