Legendary Pokémon

i am aware that blissey can learn seisnic toss but what i am unsure on is how?
Some people say you can only get it from Emerald move tutor, some say only from leaf greeen move tutor and some say both. Which is correct because i only have green and ive just caught a blissey in the safari zone. (which is hell by the way) and im considering whether i should proceed or not. Thanks in advance.

Blissey
Obviously, from any move tutor giving Seismic Toss.

We do have a Pokedex, most of the game information you might need is already in there :/