The least initial deviation from the truth is multiplied later a thousandfold.

Aristotle (384-322 BC) Greek philosopher
On the Heavens [De Caelo, Περὶ οὐρανοῦ], Book 1, ch. 5 (1.5) / 271b.9-10 (350 BC) [tr. Stock (1922)]
    (Source)

Alternate translation:

A small deviation from the truth at the beginning multiplies itself ten thousand-fold.
[tr. Hankinson (2004)]