>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.
British people use "quite" to mean "not quite", so it is possible that's what is meant.
(Reading the paragraph over though, I don't think this is the case here.)
To quote an old saying, you never miss the water 'till the well runs dry.