Carroll invented the Nyctograph and Nyctography as he was often awakened during the night with thoughts that needed to be written down at once, and didn't want to go through the lengthy process of lighting a lamp only to have to then extinguish it.

The device consisted of a gridded card with sixteen square holes, each a quarter inch wide, and system of symbols representing an alphabet of Carroll's design, which could then be transcribed the following day.

Think of the number of lonely hours a blind man often spends doing nothing, when he would gladly record his thoughts, and you will realise what a blessing you can confer on him by giving him a small ‘indelible’ memorandum-book, with a piece of paste-board containing rows of square holes, and teaching him the square-alphabet.

Carroll would enter one of his symbols in each box, then move the card down to the next line (which, in the darkness, probably, he would have to estimate) and then repeat the process.

The values were taken from his Memoria Technica, which assigned two consonants to each digit, with vowels unassigned, so that any number could be read off as a word.