One Piece Chapter 1.2, page 42: Romance Dawn (Version 2)

Luffy rides on Balloon's back as they fly through the sky. Luffy says, 'I'M THANKFUL YOU'RE BRINGING ME AND ALL, BUT ISN'T THERE A BETTER WAY TO CARRY ME? Like let me ride on your back or something.' Balloon screeches happily. A brief flashback shows Luffy's grandfather speaking to him: 'A REAL TREASURE... ISN'T A HUGE DIAMOND... IT'S NOT GOLD, SILVER, CORAL, NOR PEARLS...' Young Luffy asks, 'HUH!? IT'S NOT?' His grandfather pats Luffy's straw hat with a smile: 'NOPE! YOU'LL UNDERSTAND ONE DAY!! BUA HA HA HA HA HA!!'