Capítulo 443: Foothold.

Using a spell you had no affinity with took an obscene amount of Spirit Pressure. Sometimes, when the Mage Academy of Camelot gained a child of rare affinity, they would have no choice but to give them a teacher who might very well not have any talent in the child's field. 

In such a case, the teacher would do their best to guide the child in the fundamentals. But, even in that case, the strongest spells the teacher might cast would be Apprentice level Arts. 

However… [Float] wasn't an Apprentice level Art. In fact, it was well known as one of the most difficult to cast Magus Arts in all of Camelot. 

Not only was Leonel casting a Three Star Magus Art he had no affinity with, but he was also using it in a situation he had no business using it in.