Hi,
While looking for the source of HARD TIMES I found what is likely the lyric source of Whoa Mule. It's a song posted below by William Shakespeare Hays. I always wondered where the "Hold on to the Sleigh" line came from. Now I know!

Macon also uses this as the title to one of his songs. I believe this is of the African-American tradition as well.

WHOA! I TELL YOU! (1879)
Song & Chorus- To My Friend Chas. B. Chapman, C & M.R.R., Louisville, Ky.
Words and Music by William Shakespeare Hays, 1837-1907
Cincinnati, OH: Geo. D. Newhall & Co., 62 West 4th St.
[Source: 02567@LoC]

1. I hear dem sleigh bells ringin', De snow am fallin' fast,
I put dis mule in harness, An' got him hitch at last.
O, Lisa get your bonnet, Come and take your seat,
Grab de board you're sittin' on, An' kiver up your feet.

CHORUS Whoa! (I tell you!) Whoa! (I say!)
Keep your seat, my Liza Jane, An' hold on to de sleigh.

2. O, watch dis mule a climbin', For dis ain't half a load,
Find a mule dat's roomy, Give him all de road.
An' don't git scared at nuffin Dat you hear or see;
Liza, I'll stay wid de mule, An' you must stay wid me. (CHORUS)

3. O, see de snow a flying', Look out! let him sail,
Watch dem ears o' his'n, See him wag his tail.
Gwine to de preacher's, Liza, you keep cool,
Aint got time to kiss you now, I'm busy wid dis mule. (CHORUS)

Richie