Jonathan Swift in Gulliver's Travels , makes reference to two moons of Mars.
"The astronomers on the flying island of Laputia, have ... discovered two lesser stars, or satellites, which revolve around Mars, whereof the innermost is distant from the center of the primary exactly three of his diameters, and the outermost five: the former revolves in the space of ten hours, and the latter in twenty-one and a half. "
The number of moons is correct. The moons were not discovered till 151 years later, in 1877.
He places them in close proximity to the planet, which they are.
The moons of Mars, Phobos and Deimos, were discovered in 1877 by Asaph Hall, Sr. This was 151 years after Swift wrote Gulliver's Travels.
Swift is believed to have based his two Martian moons on a hypothesis made earlier by the German astronomer Kepler, while the accuracy of orbital details are written off by rigid thinkers as shear luck.
The accuracy of Swift's predictions they argue, suggests that he also had access to some unusually accurate data regarding Mars as well. Unusually accurate data in that he used a value for the diameter of Mars within a factor of 2 to the actual figure, while the closest factor in swifts time was within 5.