About the Classical Latin cipher
A=1, B=2, C=3, D=4, E=5, F=6, G=7, H=8, I=9, K=10, L=11, M=12,
N=13, O=14, P=15, Q=16, R=17, S=18, T=19, U=20, W=21, X=22, Y=23, Z=24.
"In 1525, Christoph Rudolff included a Classical Latin gematria cipher in his work Nimble and beautiful calculation via the artful rules of algebra [which] are so commonly called "coss", but he didn't invent it. It had been around for decades."
About the cipher used by Étienne Tabourot in 1583
A=1, B=2, C=3, D=4, E=5, F=6, G=7, H=8, I=9, K=10, L=20, M=30,
N=40, O=50, P=60, Q=70, R=80, S=90, T=100, U=200, X=300, Y=400, Z=500.
"This cipher employs units, tens and hundreds with the Latin alphabet and appeared in 1583 in the works of the French poet Étienne Tabourot. It was published or referred to in the major work of Italian Pietro Bongo ''Numerorum Mysteria,'' and a 1651 work by Georg Philipp Harsdörffer, and by Athanasius Kircher in 1665, and in a 1683 volume of ''Cabbalologia'' by Johann Henning, where it was simply referred to as the ''1683 alphabet''. It was mentioned in the work of Johann Christoph Männling ''The European Helicon or Muse Mountain'' in 1704, and it was also called the ''Alphabetum Cabbalisticum Vulgare'' in ''Die verliebte und galante Welt'' by Christian Friedrich Hunold in 1707. It was also used by Leo Tolstoy in his 1865 work ''War and Peace'' to identify Napoleon I of France with the Number of the Beast."