This article is from the Final-Fantasy and other Square Soft Games FAQ, by firstname.lastname@example.org (Nick Zitzmann) with numerous contributions by others.
Does this sound too good to be true? It's true. You just need to have a
controller with an auto-fire feature, and you must have Banon in your
First, set your cursor option to "Memory".
Second, jump onto your raft on the Lete River. On the first part of the
river, go through it as normal.
Save your game. On the second spot, at the fork in the river, if you
specify Up as your direction, the raft will go in a loop. You'll want to
go in this loop forever, so leave the direction at Up.
Now, get into a battle. Make sure Banon uses his Health command, and the
others all Fight. Turn on your controller's auto-fire on the select
button (A on the Super NES, X on the PSX). Now, turn off your monitor
and let your game run for slightly less than 24 hours. (Careful - if
you're playing the Super NES version, the Super NES sometimes locks up
if it's left running for 24 or more hours!)
When you return to your game, you'll find your characters at super-high
levels with abundant money and 99 potions.