He shall then formulate in his mind the message he wishes the reader to receive.
Let him then write upon paper a perfectly nondescript message.
While he is writing the decoy message, let him Write his hidden message upon the paper as in Explosive Runes.
This spell may be used to manipulate the unwary with hidden messages, or to communicate secretly between two Mages. The hidden message may be easily Read by a Mage proficient with Read Magic.