The Plateau–Rayleigh instability is named for Joseph Plateau and Lord Rayleigh.  In 1873, Plateau found experimentally that a vertically falling stream of water will break up into drops if its length is greater than about 3.13 to 3.18 times its diameter, which he noted is close to Pi|. Later, Rayleigh showed theoretically that a vertically falling column of non-viscous liquid with a circular cross-section should break up into drops if its length exceeded its circumference, which is indeed  times its diameter.