Mistake (contract law) void. Traditionally, Caveat Emptor (let the buyer beware), and under Common Law Caveat Venditor (let the seller beware). A contract might be voidable from unilateral mistake for any of the following: A mutual mistake occurs when the parties to a contract are both mistaken about the same "material" fact within their contract. They are at cross-purposes. There is a meeting of the minds, but the parties are mistaken. Hence the contract is voidable. "Collateral" mistakes will not afford the right of rescission. A collateral mistake is one that 'does not go to the heart' of the contract. For a mutual
Patent caveat the caveat was so abused. Gray did eventually win a judgement in a US court vindicating his claims, but long after: Bell was forever after known as inventor of the telephone. "See the articles on Gray and Bell for details." The filing fee of $10 for a caveat was less costly than the filing fee $15 for a full patent application. As stated by the USPTO: "In 1861, the fee for obtaining a full patent was $35, of which $15 was to be paid at the time of application and $20 when the patent was granted. In 1922, the patent