Static Sphere by DigitalArtPhotography
It is said that the towers of Emyn Beraid were not built indeed by the Exiles of Númenor, but were raised by Gilgalad for Elendil, his friend; and the Seeing Stone of Emyn Beraid was set in Elostirion, the tallest of the towers. Thither Elendil would repair, and thence he would gaze out over the sundering seas, when the yearning of exile was upon him; and it is believed that thus he would at whiles see far away even the Tower of Avallónë upon Eressëa, where the Master-stone abode, and yet abides. These stones were gifts of the Eldar to Amandil, father of Elendil, for the comfort of the Faithful of Númenor in their dark days, when the Elves might come no longer to that land under the shadow of Sauron. They were called the Palantíri, those that watch from afar; but all those that were brought to Middle-earth long ago were lost.
– The Silmarillion, Akallabêth