To reach and explore the Tomb of Snefaru to retrieve the artifact in Secrets of the First Pyramids in Assassin’s Creed: Origins push the statue towards the platform near the entrance:
To explore the tomb of Snefaru pull the statue towards the platform near the entrance.
Go back up and drop down onto the platform. When the platform is at ground level pull the statue onto the platform. Climb onto the statue in front of the raised platform and jump up to the raised platform:
To retrieve the artifact from the tomb of Snefaru climb onto the statue and jump up to the raised platform.