If a man should ascend alone into heaven and behold clearly the structure of the universe and the beauty of the stars, there would be no pleasure for him in the awe-inspiring sight, which would have filled him with delight if he had had someone to whom he could describe what he had seen.

[Si quis in coelum ascendisset, naturamque mundi, et pulchritudinem siderum perspexisset, insuavem illam admirationem ei fore; quae jucudissima fuisset, si aliquem, cui narraret, habuisset.]

Marcus Tullius Cicero (106-43 BC) Roman orator, statesman, philosopher
“Laelius De Amicitia [Laelius on Friendship],” ch. 23 / sec. 88 (44 BC) [tr. Falconer (1923)]
    (Source)

Original Latin. Cicero attributes this as a paraphrase of Archytas of Tarentum (d. 394 BC), a Pythagorean philosopher and astronomer. Alternate translations:

If any one could have ascended to the sky, and surveyed the structure of the universe, and the beauty of the stars, that such admiration would be insipid to him; and yet it would be most delightful if he had someone to whom he might describe it.
[tr. Edmonds (1871)]

If one had ascended to heaven, and had obtained a full view of the nature of the universe and the beauty of the stars, yet his admiration would be without delight, if there were no one to whom he could tell what he had seen.
[tr. Peabody (1887)]

If a man could ascend to heaven and get a clear view of the natural order of the universe, and the beauty of the heavenly bodies, that wonderful spectacle would give him small pleasure, though nothing could be conceived more delightful if he had but had some one to whom to tell what he had seen.
[tr. Shuckburgh (1909)]

If a man could mount to heaven and survey the mighty universe with all the planetary orbs, his admiration of its beauties would be much diminished, unless he had someone to share in his pleasure.
[Source]