Lucretius

Sed neque tam facilis res ulla est, quin ea primum
difficilis magis ad credendum constet, itemque
nil adeo magnum neque tam mirabile quicquam,
quod non paulatim minuant mirarier omnes.

For no fact is so simple we believe it at first sight,
And there is nothing that exists so great or marvelous 
That over time mankind does not admire it less and less.

Titus Lucretius Carus, De Rerum Natura (On the Nature of Things), Book II, lines 1026–1029 (tr. Stallings).