"One of the most beautiful openings. It involves the sacrifice of the King's Knight, but is not considered safe, as it is believed to admit of a perfectly satisfactory defence, and therefore to be disadvantageous to the attacking player, on account ol his having a piece less than his adversary. Nevertheless he usually gains two Pawns, a two-thirds value of the Knight given up, and the attack is very formidable, and requires great care in answering." —Henry Bird
"We could easily, and in an interesting manner, fill up a treatise on the Muzio Gambit, and even then, perhaps, we should not have said the last word. For our own part, we should just as soon play this Gambit as any other." -Isidor Gunsberg
"This brilliant Gambit was first noticed by Dr. Salvio, who states that ' the game was sent to him by Signor Muzio, who commonly won it of his adversary Don Geronimo Cascio.' The attack obtained by the sacrifice of the Knight was until recently considered irresistible." —William Cook
""The Muzio has been traced to Polerio (1590) or thereabouts. White may give up the Bishop instead of the Knight. There is nothing better for White than 5 Castles—playing for attack at all costs." —James Mason
"The surrender of the Knight at move 5 and its acceptance constitutes a variation of the King's Gambit about as favourable as any other to the first player. It is the most brilliant of all the openings, a Gambit within a Gambit, yielding an intense attack, but one which in the nature of things is unsound. The time gained is not equivalent to the force surrendered." —James Mason
"Sound or not, the Muzio Gambit will always hold a place of honour in the theory of the openings." —Saveliĭ Tartakover
After centuries of debate, the jury is still out on the Muzio's soundness. One problem is that there have been relatively few master games and the possibilities are overwhelming. My data seems to show that the Muzio is a 50-50 proposition with few draws. I interpret this as meaning the Muzio is an all-out fight on a razor-sharp playing field in which creativity and determination count for as much as theory. Below are a few such battles -
Just an interesting side note -
In 1834 La Bourdonnais defeated Alexander MacDonnell in one of chess history's most important matches. The match was well publicized and followed in the press. Joseph Méry, who in his time was a popular author/poet/playwright, wrote an epic poem, Une Revanche de Waterloo, celebrating Labourdonais' victory. Two years later Méry and Labourdonnais would found Le Palamède, the first chess magazine. That same year, Rev. Alexander Charles Louis d'Arblay (the son of the famous English novelist Fanny Burney, Madame d’Arblay) wrote an epic poem, Caïssa Rediviva, celebrating MacDonnell's heroic efforts in the match. This poem followed and recounted poetically one of MacDonnell's games, a Muzio. Rev. d'Arblay himself died the next year.
The Rev. d'Arblay also defended against a Muzio played by MacDonnell-
note: The spelling varies from MacDonnell, McDonnell or M'Donnell. Rev. d'Arblay used MacDonnell, so I did.