The members of the
first council were (probably) Gil-Galad, Elrond, Oropher, Amdir, Galadriel, Celeborn, and Cirdan. The
second council probably composed of Saruman, Gandalf, Radagast, Pallando, Alatar, Elrond, Galadriel, Celeborn, Cirdan, and Thranduil (Oropher's Son).
Whether or not Pallando, Alatar, or Radagast ever attended a meeting is debatable. However, I'm quite sure they were still standing members, even after the blue ones dissapeared.
As for Rivendell being the meeting place of the second White Council, it's possible that they always met there, but unlikely as this text suggests...
It was at the great Council held in 2851 that the "Halfling's Leaf" was first spoken of, and the matter was noted with amusement at the time, though it was afterwards remembered in a different light. The council met in Rivendell, and Gandalf sat apart, silent. but smoking prodigiously (a thing he had never done before on such an occasion), while Saruman spoke against him, and urged that contrary to Gandalf's advice Dol Guldur should not yet be molested.
-The Unfinished Tales, Part Three, The Hunt For The Ring, page 350
Taken by itself, the statement about Rivendell could lead one to think the second White Council always met there. But when you take in the full context of what the passage is saying, it implies that the Council met at Rivendell in 2851; but not always. I imagine they met often in Orthanc, Lorien, Thranduil's dwellings, Lindon, and perhaps even in Minas Tirith at times. Rivendell however, would be the ideal choice as it was in Hithaeglir at about a centerpoint in the West of Middle Earth.
On a final note, The Wise=The White Council.
Wise, The-The Istari and the greatest Eldar of Middle-Earth. 338-9, 344, 349. See White Council.
-The Unfinished Tales, Index, W, page 472
This also proves that ALL the Istari were in the council.
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