Although the exact circumstances of the shift from the ramp to the crane technology remain unclear, it has been argued that the volatile social and political conditions of Greece were more suitable to the employment of small, professional construction teams than of large bodies of unskilled labour, making the crane more preferable to the Greek polis than the more labour-intensive ramp which had been the norm in the autocratic societies of Egypt or Assyria.
The first unequivocal literary evidence for the existence of the compound pulley system appears in the Mechanical Problems (Mech.
18, 853a32-853b13) attributed to Aristotle (384–322 BC), but perhaps composed at a slightly later date.
There are also two surviving reliefs of Roman treadwheel cranes, with the Haterii tombstone from the late first century AD being particularly detailed.Heavier crane types featured five pulleys (pentaspastos) or, in case of the largest one, a set of three by five pulleys (Polyspastos) and came with two, three or four masts, depending on the maximum load.The polyspastos, when worked by four men at both sides of the winch, could readily lift 3,000 kg (3 ropes x 5 pulleys x 4 men x 50 kg = 3,000 kg).The introduction of the winch and pulley hoist soon lead to a widespread replacement of ramps as the main means of vertical motion.For the next 200 years, Greek building sites witnessed a sharp reduction in the weights handled, as the new lifting technique made the use of several smaller stones more practical than fewer larger ones.
It is mainly used for lifting heavy things and transporting them to other places.