"Neither do we find the attack upon the nature of the relief to be tenable. It was essential for plaintiff to predicate this action upon a reformation of the written instrument in order to avail himself of the right to establish an additional agreement by parol testimony, which under any other nature of proceeding might have been properly excluded on the ground that it sought to vary the terms of the written instrument." In Sibley et al vs. Pitts, 140 Or. 578, 14 P.2d 1002 we find the Supreme Court of Oregon detailing the facts in that litigation thus: "With the assistance of brokers, plaintiffs and defendant agreed that a transfer should be made by plaintiffs to defendant of certain real and personal property.