The technology of the water wheel had long been known, but it was not put into widespread use until the Middle Ages when an acute shortage of labor made machines such as the water wheel cost effective. However, the water wheels in ancient Rome and ancient China found many practical uses in powering mills for pounding grain and other substances. The Romans used both fixed and floating water wheels and introduced water power to other countries of the Roman Empire. The Romans were known to use waterwheels extensively in mining projects, with enormous Roman-era waterwheels found in places like modern-day Spain. In the 1st century BC, the Greek epigrammatist "Antipater of Thessalonica" was the first to make a reference to the waterwheel.