How do I do "what do I do here" thing #2

Hint 1 of 4:

There's only one thing you can move inside the pyramid.

Hint 2 of 4:

Push the sarcophagus feet.

Hint 3 of 4:

While you're holding the feet, send the other 2 characters up the stairs.

Hint 4 of 4:

When you let go of the feet, the stairs close.