Text from William Wade

At Dunderberg Mountain or Caldwell's Landing, what is called the Horse Race commences. This consists of an angle in the river, which for more than a mile, takes a westwardly direction, contracted to a very narrow space between bold and rocky mountains; one of which, Antony's Nose, is eleven hundred and twenty-eight feet high, and is opposite the mouth of Montgomery creek, overlooking forts Montgomery and Clinton.

Benson Lossing in The Hudson From the Wilderness to the Sea describes Dunderberg Mountain;

"Southward from Iona, on the western shore of the river, rises the rocky Donder Berg or Thunder Mountain, where, in summer, the tempest is often seen brooding. 'The captains of the river craft,' says Irving, in his legend of 'The Storm Ship', talk of a little bulbous-bottomed Dutch goblin, in trunk hose and sugar-loafed hat, with a speaking trumpet in his hand, which, they say, keeps the Donder Berg. They declare that they have heard him, in stormy weather, in the midst of the turmoil, giving orders on low Dutch, for the piping up of a fresh gust of wind, or the rattling of another thunder clap. That sometimes he has been seen surrounded by a crew of little imps, in broad breeches and short doublets, tumbling head over heels in the rack and mist, and playing a thousand gambols in the air, or buzzing like a swarm of flies about Anthony's Nose; and that, at such times, the hurry-scurry of the storm was always greatest. One time a sloop, in passing by the Donder Berg, was overtaken by a thunder-gust that came scouring round the mountain, and seemed to burst over the vessel. though tight and well ballasted, she laboured dreadfully, and the water came over the gunwale. All the crew were amazed, when it was discovered that there was a little white sugar-loaf hat on the mast-head, known at once to be the hat of the Heer of the Donder Berg. Nobody, however, dared to climb to the mast-head, and get rid of this terrible hat. The sloop continued labouring and rocking, as if she would have rolled her mast overboard, and seemed in continual danger, either of upsetting, or running on shore. In this way she drove right through the Highlands, until she had passed Pollopel's Island, where, it is said, the jurisdiction of the Donder Berg potentate ceases. No sooner had she passed this bourne, then the little hat sprung up into the air like a top, whirled up all the clouds into a vortex, and hurried them back to the summit of the Donder Berg, while the sloop righted herself, and sailed on a quietly as if in a mill-pond. Nothing saved her from utter wreck but for the fortunate circumstance of having a horse-shoe nailed against the mast- a wise precaution against evil spirits, since adapted by all the Dutch captains that navigate this haunted river"