Proposals for such inoperable [perpetual motion] machines have become so common that the United States Patent and Trademark Office (USPTO) has made an official

Proposals for such inoperable [perpetual motion] machines have become so common that the United States Patent and Trademark Office (USPTO) has made an official policy of refusing to grant patents for perpetual motion machines without a working model. The USPTO Manual of Patent Examining Practice states: With the exception of cases involving perpetual motion, a model is not ordinarily required by the Office to demonstrate the operability of a device. If operability of a device is questioned, the applicant must establish it to the satisfaction of the examiner, but he or she may choose his or her own way of so doing. https://en.wikipedia.org/wiki/Perpetual_motion#Patents https://en.wikipedia.org/wiki/Perpetual_motion#Patents