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.

My favorite Iranian poet, via an Irishman…

  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!

https://classics.mit.edu/Khayyam/rubaiyat.html

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.

here's a poem by ryokan expressing a similar sentiment

My legacy—What will it be?

Flowers in spring,

The cuckoo in summer,

And the crimson maples

Of autumn...

>"Most Beautiful Will Ever Made"

Not sure about "most" part but beautiful it absolutely is.

>I, Charles Lounsberry, being of sound and disposing mind and memory...

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