There was a tradition in Númenor that each year the king or queen would ascend to the summit of Meneltarma at three times, and there he/she would speak prayers of praise to Ilúvatar, for atop that mountain stood the Hallow of Eru.

The last of the three prayers was the Eruhantalë or the Thanksgiving to Eru which was held at the end of each fall. The king or queen would ascend the mountain, followed by his/her people who wore only white and remained completely silent. There the king or queen would recite the prayer to Eru as three Eagles of Manwë bore witness while flying overhead.
Encyclopedia entry originally written by atalante_star