During Thursday's Transfiguration class, Professor McGonagall was teaching them the Vanishing Spell, having prepared a nest of small animals in the classroom.
"The Vanishing Spell is simpler than the Summoning Charm you would normally practice at N.E.W.T. level, but it remains the most difficult magic you will encounter in your O.W.L. exams."
"I expect the essays on the Vanishing Spell I assigned previously have given you a certain understanding of the charm," Professor McGonagall said while demonstrating the incantation and wand movement.
Chapter 202