Whyte notation
The Whyte notation for classifying steam locomotives by wheel arrangement was devised by Frederick Methvan Whyte, and came into use in the early twentieth century following a December 1900 editorial in "American Engineer and Railroad Journal". The notation counts the number of leading wheels, then the number of driving wheels, and finally the number of trailing wheels, groups of numbers being separated by dashes. Other classification schemes, like UIC classification and the French, Turkish and Swiss systems for steam locomotives, count axles rather than wheels.
Laryngeal theory
This changed when Hittite was discovered and deciphered in the early 20th century. Hittite had a sound or sounds written with symbols from the Akkadian syllabary conventionally transcribed as ', as in ' "I put, am putting". This consonant did not appear to be clearly related to any of the consonants then reconstructed for PIE, and various unsatisfactory proposals were made to explain this consonant in terms of the PIE consonant system as it had then been reconstructed. It remained for Jerzy Kuryłowicz ("Études indoeuropéennes I," 1935) to propose that these sounds lined up with Saussure's conjectures. He suggested that the unknown consonant of Hittite was in fact a direct reflex of the "coefficients sonantiques" that Saussure had proposed.