the distribution of letter frequencies does not resemble that of any known language, while the small number of different letter shapes used implies that nomenclator and homophonic ciphers should be ruled out, because these typically employ larger cipher alphabets. Polyalphabetic ciphers were invented by Alberti in the 1460s and included the later Vigenère cipher, but they usually yield ciphertexts where all cipher shapes occur with roughly equal probability, quite unlike the language-like letter distribution which the Voynich manuscript appears to have. However, the presence of many tightly grouped shapes in the Voynich manuscript (such as "or", "ar", "ol", "al", "an", "ain", "aiin", "air", "aiir", "am", "ee", "eee", among others) does suggest that its cipher system may make use of a "verbose cipher", where single letters in a plaintext get enciphered into groups of fake letters. For example, the first two lines of page f15v (seen above) contain "" and "", which strongly resemble how Roman numerals such as "CCC" or "XXXX" would look if verbosely enciphered. Shorthand In 1943, Joseph Martin Feely claimed that the manuscript was a scientific diary written in shorthand. According to D'Imperio, this was "Latin, but in a system of abbreviated forms not considered acceptable by other scholars, who unanimously rejected his readings of the text". Steganography This theory holds that the text of the Voynich manuscript is mostly meaningless, but contains meaningful information hidden in inconspicuous details—e.g., the second letter of every word, or the number of letters in each line. This technique, called steganography, is very old and was described by Johannes Trithemius in 1499. Though the plain text was speculated to have been extracted by a Cardan grille (an overlay with cut-outs for the meaningful text) of some sort, this seems somewhat unlikely because the words and letters are not arranged on anything like a regular grid. Still, steganographic claims are hard to prove or disprove, because stegotexts can be arbitrarily hard to find. It has been suggested that the meaningful text could be encoded in the length or shape of certain pen strokes. Natural language Statistical analysis of the text reveals patterns similar to those of natural languages. For instance, the word entropy (about 10 bits per word) is similar to that of English or Latin texts. Amancio et al. (2013) argued that the Voynich manuscript "is mostly compatible with natural languages and incompatible with random texts". The linguist Jacques Guy once