Tall ships and tall kings
Three times three,
What brought they from the foundered land
Over the flowing sea?
Seven stars and seven stones
And one white tree.
The seven stars of Elendil’s flag refer to each of the ships of the faithful which escaped the destruction of Númenor. Each ship received a palantir. 
 The “white tree” was a fruit stolen by Isildur from the King’s Court of Numenor, which was then planted in Minas Ithil. It was a direct descendant of a model of Telperion, one of the two trees of Valinor, destroyed by Ungoliant (Shelob’s mother) at Morgoth’s behest, which gave a pure light later captured in the silmarils. 
