Metamemory

 
Prerequisite(s): Ability to cast spells that are prepared in advance, at least one other metamagic feat (See main index)
 
Benefit: Spellcasters with this feat can pay for metamagic effects by using extra levels worth of spells instead of inflating the level of spell being augmented. Doing this requires the spellcaster to use up a number of extra spell levels equal to the base level of the spell being augmented, in addition to the slots used to pay for the metamagic feats and the slot for the spell itself. Spellcasters must still decide to apply metamagic feats when they prepare their spells for the day. Spellcasters may use any combination of spell-level slots to pay for metamagic effects so long as their cumulative value equals the total level increases for the applied metamagic feats. 0th-level spells count as one-half of a spell level. Even with Metamemory, no metamagic feat can be applied to a spell if it would normally make it require higher than a 9th-level spell slot.
 
Source: Net Book of Feats