Malachi and Megaera have come up with a way to capture a fart in a jar. They say to do it in the bathtub while bathing. Fill the jar with bath water and then hold it with the open end downward. Lean back in the bathtub so that your fart bubbles will emerge in front of you rather than behind you where you can't see them. Catch the bubbles in the jar, and put the lid on the jar while it's still underwater. This way, you capture a fairly pure fart uncontaminated by atmospheric air. To enjoy your captured fart to the fullest extent, make sure that your jar does not already smell like whatever was in it before, like pickles or peanut butter.