While cleaning out my work cubicle, I came across some old Rheology Bulletins. The July 2007 issue shows a copy of the Pitch Drop Experiment at the University of Queensland. Pitch (what Americans call asphalt) was put into a funnel in 1927. The substance was allowed to sit for three years, and then the tip of the funnel was clipped. The material, with an calculated viscosity of 230 billion cP, has dripped nine times in the last 80 years. The Guinness Book of World Records identifies this as the longest experiment on record. The experiment won the 2005 Ig Nobel Prize in Physics.
Photo courtesy of Wikipedia
Hat tip: Rheology Bulletin
Update: The word "Americans" was misspelled in the original post.