The earliest libraries consisted of clay tablets found in Sumer dating back to 2600 BC containing commercial records. Private archives were also found at sites like Ugarit. Libraries grew out of record keeping in ancient Mesopotamia and Egypt. Later major libraries included the Royal Library of Ashurbanipal containing over 30,000 tablets and the great Library of Alexandria, the largest of the ancient world housing scrolls on papyrus and parchment. Private libraries emerged in Classical Greece and Rome filled with scrolls. Early classification systems were developed in China under philosophers like Laozi and scholar Liu Xiang.