“Ah state of mortal man! in time of weal,
A line, a shadow! and if ill fate fall,
One wet sponge-sweep wipes all our trace away.”
Source: Oresteia (458 BC), Agamemnon, lines 1327–1329 (tr. E. D. A. Morshead)
Original
Ἰὼ βρότεια πράγματ'· εὐτυχοῦντα μὲν σκιᾷ τις ἂν πρέψειεν· εἰ δὲ δυστυχοῖ, βολαῖς ὑγρώσσων σπόγγος ὤλεσεν γραφήν.
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Aeschylus 119
ancient Athenian playwright -525–-456 BCRelated quotes

TED Talk http://www.ted.com/talks/roger_ebert_remaking_my_voice.html (March 2011)
Context: It is human nature to look away from illness. We don't enjoy a reminder of our own fragile mortality. That's why writing on the Internet has become a life-saver for me. My ability to think and write have not been affected. And on the Web, my real voice finds expression.

“Creatures of a day! What is a man?
What is he not? A dream of a shadow
Is our mortal being.”
Pythian 8, line 95-8; pages 162-3. (446 BC)
Context: Creatures of a day! What is a man?
What is he not? A dream of a shadow
Is our mortal being. But when there comes to men
A gleam of splendour given of Heaven,
Then rests on them a light of glory
And blesséd are their days.

Song lyrics, Lionheart (1978)

Source: Prologue to Mr. Addison's Cato (1713), Line 21. Pope also uses the reference, "Like Cato, give his little Senate laws", in his Epistle to Dr. Arbuthnot (1734), Prologue to Imitations of Horace.