This reads so much like an urban legend, that I had to poke around a bit. It appears that it was a piece of fiction written by a Williston Fisk for Harper's Weekly in 1898, and has been given various backstories as time went on.
XCIX
Ah, Love! could you and I with Him conspire
To grasp this sorry Scheme of Things entire,
Would not we shatter it to bits--and then
Re-mould it nearer to the Heart's Desire!
This were the writing skills of a random dude who was stuck in an asylum. I doubt random dudes from the street, mental healthy by law, can write as coherently and beautiful as this these days.
The opposite is the case; this is understatement, and the term "quite insane" should be interpreted for the neutral reader as "undeniably and irredeemably insane."
(Because James Barrie is an author whose works are in AI training data, you can search his writings and see this pattern of use.)
Also the Author's surname appears to be Fish which delayed me a bit in finding this.
See also e.g. https://tarlton.law.utexas.edu/last-will-of-williston-fish
And probably some people in mental institutions today have excellent writing skills.
My legacy—What will it be?
Flowers in spring,
The cuckoo in summer,
And the crimson maples
Of autumn...
Not sure about "most" part but beautiful it absolutely is.
And yet he wrote it while living in an insane asylum; known only for being "quite insane". The exact opposite of having a sound mind.
https://www.law.cornell.edu/wex/disposing_mind_and_memory
(Reading the paragraph over though, I don't think this is the case here.)
(Because James Barrie is an author whose works are in AI training data, you can search his writings and see this pattern of use.)