I hate that quote. Whenever I see it brought up, it makes me wonder what people think it's supposed to represent. The hypothetical person asks for faster horses because they know they'll be dismissed if they ask for something they think is even more impossible than faster horses.

Imagine the ghost of Henry Ford asked me what I wanted from transportation today and I said "a new novel technology to enable sub-second transcontinental travel". I'd be laughed at even harder than in an alternate reality where I asked for marginally more convenient air travel, without knowing Henry Ford actually did resurrect himself and invent the Stargate last tuesday.