Able was I ere I saw Elba.
Notes from Wikiquote
Of such attributions to Napoleon, there is little credence, as stated by William Irvine in Madam I'm Adam and Other Palindromes (1987): "The well-known ABLE WAS I, ERE I SAW ELBA, for example, is conveniently attributed to Napoleon, whose knowledge of English wordplay was certainly questionable, at best." There is no mention of such a palindrome in O'Meara's own work, Napoleon in Exile : or, A Voice from St. Helena (1822).