Level 1
In the section with the water, break the far right block and kneel on the one below it. A money bag will appear.
When you first enter the game, walk left until you reach the door. Normally the door pulls you in. If you jump the door a money bag will appear on the other side. Remember to jump over the door again.

Level 2
On the first screen, climb the stairs, break the wall on the right, and enter the space that is created. A crown will appear.

Level 2 (Second part, just after the Medusa heads disappear)
Stand on the pair of blocks that are slightly above the rest for a few seconds without kneeling. A treasure chest will appear.

Level 3 (First part).
After climbing the stairs, go to the right edge of the lowest level of blocks and kneel. A money bag will appear.

Level 3 (Second part)
After climbing the stairs, kneel above the pair of blocks that are not reachable for a money bag.