Bip-39. From this position ahead the seed could possibly be prepared on paper or spoken around telephone which opened up new, Actual physical ways of backing up the seed (a number of paper copies in different spots, tough copies on steel plates with further protection from hearth/flood and so on.). https://financemarker94837.wikijm.com/1101362/the_anatomy_of_a_bip39_phrase_entropy_terms_and_safety