The cat's name is written in hieroglyphics on a plaque in the drawer that opened when you solved the scale puzzle. You can't take it with you, so either draw a picture of the glyphs or take a picture with your cell phone.
Now go back to the hall that leads to the golden sarcophagus and step on the stones that make up the cat's name in glyphs.
The first glyph on the plaque is a square with the bottom open; I understand it means "house." So look for a stone in the floor that looks like that, and step on it.
Next is a picture of a cat, so step on the cat stone. And so on.
This is much easier than it sounds, as long as you have a picture of the cat plaque to refer to. In any one scene you're in, there will only ever be one right stone to step on. And when you're done, you've reached the golden sarcophagus -- and you'll never have to do THAT again.