On the rough path leading toward Sleeping Tree Camp is a group of standing stones and three Nordic Puzzle Pillars. Next to the puzzle is a closed grate on top of a caved-in ruin. Solving the puzzle and activating the handle unlocks and opens the grate allowing access down the spiral staircase to a skeleton and a chest.
The solution of the puzzle is Whale, Eagle, Snake (from left to right if standing by the lever, as shown in the picture). After rotating the symbols, activate a handle to finally open the grate. The symbols to solve the puzzle must face this handle, not the grate, or it will not open.
- As of the 1.8 update, and installation of Dawnguard, Hearthfire, and Dragonborn, the chest has proven to be safe. Items were stored there for three to four in-game months before update, and were still safe afterwards. A Hypothetical Treachery will respawn if taken, but this does not appear to affect stored items.