This text comes from The Poetical Works of Robert Burns, a historical songbook transcribed on Wikisource and reproduced from the pinned revision linked below.
Mossgiel — 1786.
Sir,
Yours this moment I unseal,
And faith I am gay and hearty!
To tell the truth an' shame the Deil
I am as fu' as Bartie:
But foorsday Sir, my promise leal
Expect me o' your party,
If on a beastie I can speel,
Or hurl in a cartie.R. B.