Yes Elendil had 3 in Arnor, and Isildur and Anarion, joint rulers of Gondor under Elendil had 4. Here is a quote:
"Three Elendil took, and his sons each two. Those of Elendil were set in towers upon Emyn Beraid, and upon Amon Sûl, and in the city of Annúminas. But those of his sons were at Minas Ithil and Minas Anor, and at Orthanc and in Osgiliath. Now these Stones had this virtue that those who looked therein might perceive in them things far off, whether in place or in time. For the most part they revealed only things near to another kindred Stone, for the Stones each called to each; but those who possessed great strength of will and of mind might learn to direct their gaze whither they would. Thus the Númenóreans were aware of many things that their enemies wished to conceal, and little escaped their vigilance in the days of their might." The Silmarillion
Over the second and third ages they were lost:
"They were called the Palantíri, those that watch from afar; but all those that were brought to Middle-earth long ago were lost."
Originally all seven Palantir were given to the Edain in Numenor as gifts and the master stone was kept in Tol Eressea beyond the sea.
There was one that was captured by the Nazgul from Minas Morgul. Tha is the one Sauron used to keep in touch with saruman. BTW it never said how Saruman dicovered the Palantir hidden in Orthanc?
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"Thou living fool. No man may hinder me."-Witch King of Angmar
The one from Osgilliath was the major one among the palantiri, but also the first one to be lost. During the civil war of the Kinstrife around the middle of the Third Age, it fell into the river Anduin. And there was another Stone that was placed in the tower of Elostirion in the Towerhills, just west of the Shire near the Grey Havens. Until it was taken back to the West with the three Elves and Gandalf when they returned to the Blessed Realm. Which stone was it that drove Denethor mad? WHere was it placed originally?
-- Edited by ArwenLegolas at 04:06, 2007-04-12
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Hey dol! merry dol! ring a dong dillo! Ring a dong! hop along! fal lal the willow! Tom Bom, Jolly Tom, Tom Bombadillo!
As I already said, just click on the linky in my previous post, and you find a detailed article on palantiri, underneath information on each stone. It is a much better account then what I could post here, and it helps me save some time. Just a short answer... Saruman found it there because nobody ever took it away from Orthanc, actually the Palantir was the main reason he desired to reside in Orthanc. The stone that drove Denethor mad was the Anor-stone, that always remained in Minas Anor/Tirith
The site is one of my favourites. The Encyclopedia of Arda is indeed larger and has more names that you can search through, on the other hand many of their entries are very short. Tuckburough on the other hand might have less names, however their entries are very well researched. For example you also have complex information on the Palantiri from the Unfinished Tales, which is not present on the EoA.