Multiple wheels in a pulley system allow more weight to be lifted.
The pulley was an advancement on the technology of the wheel that allowed great weights to be lifted with little force. Although nobody can say for certain when or where the pulley was invented, the Greeks can claim credit for the earliest known written mention of such a device, in a text from the 4th century B.C.
The famous Greek mathematician Archimedes is credited with dozens of discoveries and inventions, including the compound pulley, in which combinations of pulleys allow objects of great size and weight to be moved. In his account of the life of Marcellus, Plutarch describes how Archimedes used a system of compound pulleys to enable himself to move a three-masted merchant ship that had been placed on dry land and then loaded down with passengers and freight. Archimedes is supposed to have made his famous remark, that he could move the entire earth if given the right place to stand, in connection with this feat.
Harmon, Beau. "Ancient Greek Invention of the Pulley." Synonym, https://classroom.synonym.com/ancient-greek-invention-pulley-9468.html. Accessed 18 April 2019.