Hesiod, Theogony

Then Zeus no longer held back his might; but straight his heart was filled with fury and he showed forth all his strength. From Heaven and from Olympus [690] he came immediately, hurling his lightning: the bolts flew thick and fast from his strong hand together with thunder and lightning, whirling an awesome flame. The life-giving earth crashed around in burning, and the vast wood crackled loud with fire all about. [695] All the land seethed, and Ocean's streams and the unfruitful sea. The hot vapor lapped round the earthborn Titans: flame unspeakable rose to the bright upper air: the flashing glare of the thunderstone and lightning blinded their eyes for all that they were strong. [700] Astounding heat seized Chaos: and to see with eyes and to hear the sound with ears it seemed even as if Earth and wide Heaven above came together; for such a mighty crash would have arisen if Earth were being hurled to ruin, and Heaven from on high were hurling her down; [705] so great a crash was there while the gods were meeting together in strife. Also the winds brought rumbling earthquake and duststorm, thunder and lightning and the lurid thunderbolt, which are the shafts of great Zeus, and carried the clangor and the warcry into the midst of the two hosts. A horrible uproar [710] of terrible strife arose: mighty deeds were shown and the battle inclined. But until then, they kept at one another and fought continually in cruel war. And amongst the foremost Cottus and Briareos and Gyes insatiate for war [715] raised fierce fighting: three hundred rocks, one upon another, they launched from their strong hands and overshadowed the Titans with their missiles, and hurled them beneath the wide-pathed earth, and bound them in bitter chains when they had conquered them by their strength for all their great spirit, [720] as far beneath the earth as heaven is above earth; for so far is it from earth to Tartarus. For a brazen anvil falling down from heaven nine nights and days would reach the earth upon the tenth: and again, a brazen anvil falling from earth nine nights and days [725] would reach Tartarus upon the tenth. Round it runs a fence of bronze, and night spreads in triple line all about it like a neck-circlet, while above grow the roots of the earth and unfruitful sea.