May 29: Ancient lava stone table with reflecting pool - a navigation aid, I was told. Easier to trace constellations in water than in the sky. From this angle it's hard to tell, but it was balanced on three stone legs, and the whole table was about one meter across. I do not know the Hawai'ian name for it, but this one was on the beach near 'Ahu'ena Heiau in Kona.
Modern navigation note: my GPS reading for the location: N 19° 38.389' W 155° 59.856'.