the beginning of the Warring States period (403–221 BC); to operate the trebuchet, a team of men pulled on ropes attached to the butt of the shorter segment of a long wooden beam separated by a rotating axle fixed to a base framework, allowing the longer segment of the beam to lunge forward and use its sling to hurl a missile; by the 9th century a hybrid of the traction and counterweight trebuchet, employing manpower and a pivoting weight, was used in the Middle East, Mediterranean Basin, and Northern Europe; by the 12th century, the full-fledged counterweight trebuchet was developed under the Ayyubid dynasty of Islamic Syria and Egypt (described by Mardi bin Ali al-Tarsusi) and used in the Third Crusade; by the 13th century, the counterweight trebuchet found its way into Song Dynasty (960–1279) China via the Mongol invaders under Kublai Khan (r. 1260–1294) who used it in the Siege of Xiangyang (1267–1273). Trip hammer: The ancient Chinese used pestle and mortar to pound and decorticate grain, which was superseded by the treadle-operated tilt hammer (employing a simple lever and fulcrum) perhaps during the Zhou Dynasty (1122–256 BC) but first described in a Han Dynasty (202 BC – 220 AD) dictionary of 40 BC and soon after by the Han dynasty philosopher and writer Yang Xiong (53 BC – 18 AD) in his Fangyan dictionary written in 15 BC; the next stage in this evolution of grain-pounding devices was to apply hydraulic power, which the Han dynasty philosopher and writer Huan Tan (43 BC – 28 AD) mentioned in his Xinlun of 20 AD, although he also described trip hammers powered by the labor of horses, oxen, donkeys, and mules. After Huan Tan's book was written, numerous references to trip hammers powered by waterwheels were made in subsequent Chinese dynasties and in Medieval Europe by the 12th century. However, trip hammers were also attested by both literary (Pliny, Natural History 18.97) and archaeological evidence in fairly widespread use in the Roman Empire by the 1st century AD. Tuned bells: The earliest complete set of tuned bells, sixteen in all, were found in Tomb 8 of Marquis Su of Jin at Qucun, southern Shanxi. The tomb has been dated by AMS radiocarbon techniques to 815–786 BC, during the period of the Zhou Dynasty. Of the sixty-four bronze bells found in the tomb of Marquis Yi of Zeng interred by 433