Examine the scale; take the BIRD SEED (R) and the PICTURE^SLIDE (S).
Select the metal star (T).
Take the RAINBOW COAL (U) and the RUST REMOVER (V).
Return to the River.
Examine the hand and use the RUST REMOVER on the spikes (W); take the METAL SPIKES (X).
Return to the Gazebo.
Examine the gazebo; place the METAL SPIKES on the stone to activate a puzzle (Y).
To solve the puzzle, swap the clock hand positions until every hand is visible.
Please see the screenshot for the solution (Z).
Take the GLOWING CRYSTAL (A).