Historic homes were built before air conditioning and builders needed ways to keep them cool. One of the ways this was done was with vent locks.
Wooden window vent locks are a historic hardware that will let you lock your windows BUT in the open position.
These are great. Using these locks you can leave your windows “locked” open when you are away or even while sleeping. They are wonderful for summer days.
Below are links to some vent locks if you want to order online: