Advice iz like kastor-ile, eazy enuff to give, but dredful uneazy tew take.

[Advice is like castor oil, easy enough to give, but dreadfully uneasy to take.]

Josh Billings (1818-1885) American humorist, aphorist [pseud. of Henry Wheeler Shaw]

Everybody’s Friend, Or; Josh Billing’s Encyclopedia and Proverbial Philosophy of Wit and Humor, ch. 148 “Affurisms: Ink Brats” (1874)
    (Source)

The phrase also shows up twice in Wit and Wisdom of Josh Billings (1913) [ed. H. Montague] (which, being published in England, did away with the misspellings):

Advice is like castor oil -- easy enough to give but dreadful hard to take.
["Advice"]

Advice is like castor oil -- awful easy to give but mighty hard to take.
["How to Select a Husband"]