Well first there’s the cutting technology. Scything is ancient. Industrial production of push mowers using cylinder blades were developed in the 1800s and the more modern gas powered rotary cutters came along in the 19th century with many other self-propelled and automated mechanisms. This started with coal and wood fired agricultural equipment used for processing, like threshing and winnowing. As internal combustion engines (gas powered) developed in the 20th century more equipment and processes could be incorporated on-site and in-field.