How do you get a heavy ball in Pokemon Emerald?

In Pokemon Emerald, to obtain a Heavy Ball, you need to visit the Safari Zone extension in the Hoenn region. The Heavy Ball is a special type of Poke Ball that is more effective at catching heavier Pokemon. You can receive the Heavy Ball as a prize for participating in the Safari Zone's catching contest or by talking to the Safari Zone Warden after catching a certain number of Pokemon in the Safari Zone.