From Final Fantasy Wiki

The Snowcraft is a means of transportation in Final Fantasy II. For a long time, it was hidden by Josef, stashed away in a hidden room in the Semitt Falls Cave. The Snowcraft is required to cross the Snowfield and reach the Snow Cave.

In the Final Fantasy Origins and most recent remakes, there is a memory minigame that can be played if the player holds A and presses B 22 times while riding the Snowcraft. The awards that can be won in the game are changed if the player can get the level of their Frog spell to 16, and consist of late-game rare items, such as Genji Gear and Masamunes.