The Spritsail rig.
Without doubt the spritsail rig is, next to lateen rig and junk rig, one of the oldest types of fore-and-aft rig; one of the earliest depictions of it is Roman, from the 3rd. century A.D., see: http://en.wikipedia.org/wiki/Spritsail.
Because the sprit is on the starboard side of the mainsail, the sail is deformed on port tack by wind pressure, so the faster and higher is the starboard tack. This is probably the reason why, on collision course, the ship on port tack gives way to the ship on starboard tack.
One of the best-known English ships propelled by a spritsail rig is the Thames sailing barge, http://en.wikipedia.org/wiki/Thames_sailing_barge, of which luckily some have survived the years, lovingly restored by their owners.
In Holland also remain some types of boats and ships, mostly fishermen, driven by spritsail rig. The picture above is of one of those.