A stiff drink, kind of like a Martini, but golden.
Also listed in David Embury’s “The Fine Art of Mixing Drinks”, the history is somewhat interesting. From the source of all facts, wikipedia:
“A popular history suggests that the drink originated at the Manhattan Club in New York City in the early 1870s, where it was invented by Dr. Iain Marshall for a banquet hosted by Jennie Jerome (Lady Randolph Churchill, Winston’s mother) in honor of presidential candidate Samuel J. Tilden. The success of the banquet made the drink fashionable, later prompting several people to request the drink by referring to the name of the club where it originated—”the Manhattan cocktail”. However, Lady Randolph was in France at the time and pregnant, so the story is likely a fiction. The original “Manhattan cocktail” was a mix of “American Whiskey, Italian Vermouth and Angostura bitters”