Aus Kouli's FAQ:
(IIRC, des Rätsels Lösung ist "Schalter gemäss Hint, aber von Sonnenuntergang nach Sonnenaufgang... also umgekehrt, von rechts nach links statt von links nach rechts" oder sowas in der Art):
Once you are ready, get back down and enter the Trial Cave. You can take the middle door. Within, explore for Stone Check and ?Item. To move on, keep going to the north and save the game.
There are seven doors:
Door 1 - 2 - 3 - 4 - 5 - 6 - 7
Go in Door 1, 3, 5 and 6 to hit the switches down. Make sure the switches in
2 and 7 are all up. After, go down from the center. You will fight Peryton and 3 Whispers. Go on and you will get the Van Emblem, as well as the Shiseijuu Ougi. Pick the first choice and exit out once you are ready.