In C.I.T. Corporation v. Panac (1944) 25 Cal.2d 547, the court explained: "'Though manifestation of assent and not actual assent creates a contract, a writing purporting to be a contract and not ambiguous in its language may be wholly void. If without negligence on his part, a signer attaches his signature to a paper assuming it to be a paper of a different character, the paper is void. Such a mistake as to the character of the instrument may relate to its existence as a contract or legally operative document of any kind, or to whether it is the kind of contract or legal document which it purports or is represented to be.'"