The Mechtnon System for Number Memorization This system was developed by Mike Mechtnon in 1990. It is described in the book "Esels Welt: Mnemotechnik zwischen Simonides und Harry Lorayne" by Ulrich Voigt. Click here to see his website (in German). The system works with "Houses" and "Categories" in the following way: There are 100 houses, which are "imbued" with reasonably sufficient emotional or phenomenological difference to be able to discern them. They are seen as the Great (As in Great, not as in Big) House, the Old Red One or something similar and better. Every house has assigned to it a number from 00 to 99. In each "House" there is play, a story, a dynamical event consisting of 25 persons or objects interacting. Each of the participants is from one of 25 separate "Categories" (Famous persons, plants, animals, ...). Every category has 100 elements, assigned, if I remember correctly, by way of the Master System. Now comes an important point: The system allows the user to be able to instantly say which number there is on a given position of Pi in an intervall ranging from 0 to 9.999. This is done this way: 100 houses with 25 category elements = 2.500 elements = 5.000 digits. So there are 200 houses. Every house stands for a "block" of Pi having 500 digits. So when the user is asked which digit there is on the 3761th place, the procedure is the following: Since 3761 is part of the first 5.000, you go to the first 100 houses. Specifically to house number 74. (Explanation: Since there are only 25 categories, every house can only cover 25x2=50 digits. So two houses cover one 100-leap. 61 is in the second half of the 100-range covered by houses 73 and 74. So it is house 74. Excourse: Another way might be to have two houses with 37, one in the first 100 houses, one in the seond 100 houses. Then: The first two digits are 37, so it is a "37"-house. 61 is in the second part of 100, so it is the 37 house in the second 100 houses. This might have the slight disadvantage that you had to keep pairs of same numbered houses apart, but this might be easier than thought.) Now comes the interesting part: All categories have a firmly assigned order, so the element covering digits 11 and 12 and 61 and 62 always share the same category (a great advantage of this internal structure is that, apart from the house itself, you can completely neglect any local order for the images, making interactions much freer and less artificial. The category of the element intrinsically has all necessary information, so you have order without order.) With some practice it would perhaps be clear that: 61 is always covered by an element from the plant category. So the question is: Which plant is in house 74? It might be a daffodil. This would be 18 according to the classical system. Since this image encodes places 61 and 62, the sought number is 1. I am sure that this seemingly long process can be made much faster by practice, since it is mainly pattern recognition and search, similar to the Doomsday method (or which one you prefer) for the search of the day for a calendar date. So, this was his use (which might be made even quicker by choosing 50 categories and 100 houses, since the process is much more linear.). The proposed use for speed memorization with a four-digit-system is maybe: 100 houses, 100 categories: In every house there is different element from a category, perhaps in accordance with the house itself: In the hunting house (Let us say nr. 36) the category animal might be a fox or a hunting dog. This seems like a quite improved SEM. The problem might be that there is too much visual "prelude" before arriving at the image, rather that simply using a abstract letter conversion of the numbers for the categories and that you will have to get to the image in the house, take it from there and put it somewhere else every time. As a conclusion, I think there are two basic ways to create a category based four-digit-system: 1. The first two digits are the category, the last two are the concrete image. 2391: 23 = animal (category), so 91 = "cat" (concrete image) Here the image itself is bound to the letter system. 2. The first two are a theme, the next two are the category: 6567: 26 = Poseidon's lair (theme) 67 = plant (category), leading, according to each one's association, perhaps to "coral". Here the image is not bound to the letter system. By the way, I do not think that not being able to go through all the images might be such a problem: It could well be that one experiences that running through all the 100 categories (or themes) will ring a bell as well or even better, and then all that remains is searching in your 100-element subcategory. ` `