what strange fact was reveled to gulliver by an eminent person at court

Gulliver was apprised of the fact that his visions of immortality were far different than the reality.

At last, the same gentleman who had been my interpreter, said, "he was desired by the rest to set me right in a few mistakes, which I had fallen into through the common imbecility of human nature, and upon that allowance was less answerable for them. That this breed of struldbrugs was peculiar to their country, for there were no such people either in Balnibarbi or Japan, where he had the honour to be ambassador from his majesty, and found the natives in both those kingdoms very hard to believe that the fact was possible: and it appeared from my astonishment when he first mentioned the matter to me, that I received it as a thing wholly new, and scarcely to be credited. That in the two kingdoms above mentioned, where, during his residence, he had conversed very much, he observed long life to be the universal desire and wish of mankind. That whoever had one foot in the grave was sure to hold back the other as strongly as he could. That the oldest had still hopes of living one day longer, and looked on death as the greatest evil, from which nature always prompted him to retreat. Only in this island of Luggnagg the appetite for living was not so eager, from the continual example of the struldbrugs before their eyes.