Since the sword and the jewel are considered sacred objects, they are considered to move to the new Emperor on their own, so the expression used is 'togyo' (an honorific term for 'transfer' of gods or Emperors).
神体である剣と璽が新帝の下に自ら動くという建前から「渡御」（神・天皇等が「渡る」ことをいう尊敬語）という表現がとられる。