Mage Knight: Machination
Prerequisites: Knowledge (Arcana): 4 ranks, must know at least one Summon Golem cantrip.
Benefits: You may “lose” a prepared cantrip of the same level or higher than a Summon Golem cantrip in order to summon a golem without preparing ahead of time. This feat only applies to the versions of Summon Golem you are able to prepare (in other words, if Summon Golem I was one of your known cantrips but Summon Golem II was not, you could spontaneously cast Summon Golem I but would be unable to spontaneously cast Summon Golem II).
Normal: A magus must prepare all of his cantrips ahead of time.