The Silmarillion

Thus the years passed, and while Middle-earth went backward and light and wisdom faded, the Dúnedain dwelt under the protection of the Valar and in the friendship of the Eldar, and they increased in stature both of mind and body. For though this people used still their own speech, their kings and lords knew and spoke also the Elven tongue, which they had learned in the days of their alliance, and thus they held converse still with the Eldar, whether of Eressëa or of the west-lands of Middle-earth. And the loremasters among them learned also the High Eldarin tongue of the Blessed Realm, in which much story and song was preserved from the beginning of the world; and they made letters and scrolls and books, and wrote in them many things of wisdom and wonder in the high tide of their realm, of which all is now forgot. So it came to pass that, beside their own names, all the lords of the Númenóreans had also Eldarin names; and the like with the cities and fair places that they founded in Númenor and on the shores of the Hither Lands.

For the Dúnedain became mighty in crafts, so that if they had had the mind they could easily have surpassed the evil kings of Middle-earth in the making of war and the forging of weapons; but they were become men of peace. Above all arts they nourished shipbuilding and sea-craft, and they became mariners whose like shall never be again since the world was diminished; and voyaging upon the wide seas was the chief feat and adventure of their hardy men in the gallant days of their youth.

But the Lords of Valinor forbade them to sail so far westward that the coasts of Númenor could no longer be seen; and for long the Dúnedain were content, though they did not fully understand the purpose of this ban. But the design of Manwë was that the Númenóreans should not be tempted to seek for the Blessed Realm, nor desire to overpass the limits set to their bliss, becoming enamoured of the immortality of the Valar and the Eldar and the lands where all things endure.

For in those days Valinor still remained in the world visible, and there Ilúvatar permitted the Valar to maintain upon Earth an abiding place, a memorial of that which might have been if Morgoth had not cast his shadow on the world. This the Númenóreans knew full well; and at times, when all the air was clear and the sun was in the east, they would look out and descry far off in the west a city white-shining on a distant shore, and a great harbour and a tower. For in those days the Númenóreans were far-sighted; yet even so it was only the keenest eyes among them that could see this vision, from the Meneltarma, maybe, or from some tall ship that lay off their western coast as far as it was lawful for them to go. For they did not dare to break the Ban of the Lords of the West. But the wise among them knew that this distant land was not indeed the Blessed Realm of Valinor, but was Avallónë, the haven of the Eldar upon Eressëa, easternmost of the Undying Lands. And thence at times the Firstborn still would come sailing to Númenor in oarless boats, as white birds flying from the sunset. And they brought to Númenor many gifts: birds of song, and fragrant flowers, and herbs of great virtue. And a seedling they brought of Celeborn, the White Tree that grew in the midst of Eressëa; and that was in its turn a seedling of Galathilion the Tree of Túna, the image of Telperion that Yavanna gave to the Eldar in the Blessed Realm. And the tree grew and blossomed in the courts of the King in Armenelos; Nimloth it was named, and flowered in the evening, and the shadows of night it filled with its fragrance.

Thus it was that because of the Ban of the Valar the voyages of the Dúnedain in those days went ever eastward and not westward, from the darkness of the North to the heats of the South, and beyond the South to the Nether Darkness; and they came even into the inner seas, and sailed about Middle-earth and glimpsed from their high prows the Gates of Morning in the East. And the Dúnedain came at times to the shores of the Great Lands, and they took pity on the forsaken world of Middle-earth; and the Lords of Númenor set foot again upon the western shores in the Dark Years of Men, and none yet dared to withstand them. For most of the Men of that age that sat under the Shadow were now grown weak and fearful. And coming among them the Númenóreans taught them many things. Corn and wine they brought, and they instructed Men in the sowing of seed and the grinding of grain, in the hewing of wood and the shaping of stone, and in the ordering of their life, such as it might be in the lands of swift death and little bliss.