What are the criteria for determining if an invention was “on sale” under pre-AIA law?

Under pre-AIA law, the criteria for determining if an invention was “on sale” were established in the Pfaff v. Wells Electronics, Inc. case. The MPEP summarizes these criteria as follows:

“The pre-AIA case law indicates that on sale activity will bar patentability if the claimed invention was: (1) the subject of a commercial sale or offer for sale, not primarily for experimental purposes; and (2) ready for patenting.”

These criteria are still relevant for understanding “on sale” activities under AIA, as the meaning of the term has not been significantly altered.