Try the Timer Ball.
You can catch MEWTWO ,not Mewto, at the end of Cerulean cave
you cant catch mewtwo in Pokemon platinum peral diamond you can in Pokemon heart gold and solsilver in canalave cave
there is absolutely no secret apricorn in heart gold or soul silver, but good question.
U can't in heart gold but u can catch mewtwo
-Golden Feather -Bell -Kimono Girls -Master Pokeball (WILL NOT FAIL AT ANY CATCH ALAWAYS WILL CATCH POKEMON)
There is no purple apricorn in Heart Gold. There is blue and red, but not purple.
Mew can't be catched in Pokemon heartgold, only mewtwo.
You can find Kurt in Azalea Town! He can also make you Pokeballs made also ...Red Apricorn - Level BallGreen Apricorn - Friend BallWhite Apricorn - Fast BallBlack Apricorn - Heavy BallPink Apricorn - Love BallYellow Apricorn - Moon BallBlue Apricorn - Lure Ball
Other than the masterball try using a lot of ultra balls.
A Dark Ball could work nicely here, since you're in a cave.
A Master ball is the best pokeball in the history of Pokemon. You may not have 900 masterballs like i do, but if you purchase an action replay which they sell at target for $20, it comes with a cheat to get all pokeballs x 900. that is the best way to catch every Pokemon there is.
You can get Latias? Oh right! Use a masterball for a guarantee catch, if you are a button masher use any pokeball.