The falling sky clause occurs in a passage of Heauton Timorumenos, by Terence, suggesting that it was a common saying in his time. In the scene, Syrus suggests a scheme through which Clinia might deceive another into taking actions that would further his love interests. Syrus lays out his plan, while Clinia, who must act it out, finds faults with it, finally asking, "Is that sufficient? If his father should come to know of it, pray, what then?" To which the Syrus replies, "Quid si redeo ad illos qui aiunt, 'Quid si nunc cœlum ruat?'"—"What if I have recourse to those who say, 'What now if the sky were to fall?'", the suggestion being that Clinia has no other options available, so to worry that the plan will, obviously, fail if the father finds out makes no more sense than worrying about the fact that it will also fail if the world were to suddenly end.
This concern recalls a passage in Arrian's Campaigns of Alexander, Book I, 4, where ambassadors of the Celtae from the Adriatic sea, tall men of haughty demeanor, upon being asked by Alexander what in the world they feared most, answered that their worst fear was that the sky might fall on their heads. Alexander, who hoped to hear himself named, was disappointed by an answer that implied that nothing within human power could hurt them, short of a total destruction of nature.
In a similar vein, Theognis of Megara urges "May the great broad sky of bronze fall on my head / (That fear of earth-born men) if I am not / A friend to those who love me, and a pain / And irritation to my enemies." Whereas Aristotle asserts in his Physics, B. IV, that it was the early notion of ignorant nations that the sky was supported on the shoulders of Atlas, and that when he let go of it, it would fall.
On the other hand, Horace opens one of his odes with a depiction of a Stoic hero who will submit to the ruin of the universe around him: "Si fractus illabatur orbis, / impavidum ferient ruinae"—"Should the whole frame of Nature round him break, / In ruin and confusion hurled, / He, unconcerned, would hear the mighty crack, / And stand secure amidst a falling world." (Odes 3.3.7-8, translated by Joseph Addison.)
In De Ira (On Anger), Book I, Chapter XVIII, Seneca tells of Gnaeus Calpurnius Piso, a Roman governor and lawmaker, when he was angry, ordering the execution of a soldier who had returned from a leave of absence without his comrade, on the grounds that if the man did not produce his companion, he had presumably killed the latter. As the condemned man was presenting his neck to the executioner's sword, there suddenly appeared the very comrade who was supposedly murdered. The centurion overseeing the execution halted the proceedings and led the condemned man back to Piso, expecting a reprieve. But Piso mounted the tribunal in a rage, and ordered the three soldiers to be executed. He ordered the death of the man who was to have been executed, because the sentence had already been passed; he also ordered the death of the centurion who was in charge of the original execution, for failing to perform his duty; and finally, he ordered the death of the man who had been supposed to have been murdered, because he had been the cause of the death of two innocent men.