Maggie Stiefvater said this quote
“ Adam was in the dream, too; he traced the tangled pattern of ink with his finger. He said, Scio quid hoc est. As he traced it further and further down on the bare skin of Ronan's back, Ronan himself disappeared entirely, and the tattoo got smaller and smaller. It was a Celtic knot the size of a wafer, and then Adam, who had become Kavinsky, said Scio quid estis vos. He put the tattoo in his mouth and swallowed it.Ronan woke with a start, ashamed and euphoric.The euphoria wore off long before the shame did.He was never sleeping again. ”