Massive (Quality)
A weapon with the massive quality requires a minimum Strength score of 18 to wield with proficiency. It may not be concealed through mundane means, and cannot be sheathed without a full-round action to stow in a suitably-sized pack or roll. If it is stowed in such a way, it requires another full-round action to fish it back out.
Massive weapons cannot be drawn from storage as part of a move action, nor do they benefit from the quick draw feat. Magic packs, such as the Handy Haversack still require a full-round action for retrieval, not because the pack fails to offer up the weapon but because a great deal of care must be taken to prevent the weapon from gratuitously removing the wielder's limbs when retrieving it.
For these reasons, massive weapons are nearly always carried in hand, balanced on a shoulder, which is when they normally gain the Handy quality. This makes it much easier to get a Massive weapon into action in a fight, at the considerable cost of leaving the wielder with only one free hand outside of combat.
Massive weapons may never be wielded one-handed in combat, even if the weapon is one size smaller, or the wielder possesses a feat which would normally allow such a thing.