A spray bottle filled with water. Right hand on the bottle, left on cable release to trigger camera on tripod. Moderate wide-angle, 24mm.
Lighting: A flash (optically triggered) with cardboard shoot behind me about 30 degrees camera left, to light up hand, bottle and wall. My home-made flash (triggered by PC cord) on a tripod below where the spray would be, to light up the water droplets in the air. Had I more time, I would have devised a way to place the second flash above the stream, so it would light the top of the stream as opposed to the bottom.
Post processing: Cloned out some mysterious lens flare (?), as well as a few renegade droplets in the top right that managed to get lit magically. Black and white conversion, channel mixer with 50% red, 50% green and 25% blue.