The greatest follies, like the stoutest ropes, are often composed of a multitude of strands. Take the cable thread by thread, take separately each petty determining motive, and you can snap them one by one and say, “There’s no more to it than that!” Braid them and twist them together, and what you have is momentous.
 
[Les fortes sottises sont souvent faites, comme les grosses cordes, d’une multitude de brins. Prenez le câble fil à fil, prenez séparément tous les petits motifs déterminants, vous les cassez l’un après l’autre, et vous dites: Ce n’est que cela! Tressez-les et tordez-les ensemble, c’est une énormité.]

Victor Hugo (1802-1885) French writer
Les Misérables, Part 2 “Cosette,” Book 5 “Dark Hunt, Mute Mutts,” ch. 10 (2.5.10) (1862) [tr. Donougher (2013)]
    (Source)

(Source (French)). Alternate translations:

Great blunders are often made, like large ropes, of a multitude of fibres. Take the cable thread by thread, take separately all the little determining motives, you break them one after another, and you say: that is all. Wind them and twist them together, they become an enormity.
[tr. Wilbour (1862)]

Great follies are often made, like stout ropes, of a multitude of fibers. Take the cable, thread by thread, catch hold of the small determining motives separately, and you break them one after the other, and say to yourself, “It is only that”; but twist them together and you have an enormity.
[tr. Wraxall (1862)]

The greatest follies are often composed, like the largest ropes, of a multitude of strands. Take the cable thread by thread, take all the petty determining motives separately, and you can break them one after the other, and you say, "That is all there is of it!" Braid them, twist them together; the result is enormous.
[tr. Hapgood (1887)]

The greatest blunders, like the thickest ropes, are often compounded of a multitude of strands. Take the rope apart, separate it into the small threads that compose it, and you can break them one by one. You think, 'That is all there was!' But twist them all together, and you have something tremendous.
[tr. Denny (1976)]

Great blunders are often made, like large ropes, of a multitude of fibers. Take the cable thread by thread, take all the little determining motives separately, you break them one after another, and you say: That is all it is. Braid them and twist them together, they become an enormity.
[tr. Wilbour/Fahnestock/MacAfee (1987)]