Spanish galleons by Pieter Bruegel (c. 1528 - 1569).
Reefing is done with bonnets, parts of the lower sails that can be unlaced and removed. Sails are taken in either by lowering the yard down to the top as has been done on the ship at left, with her topsails, or by lowering the lower yards to the deck - there were no footropes.
Cool fellow the one playing his harp in the nude at lower right.
