I already had this on my web site before I started this blog, but I realized today that I have no link to it anymore (and I am very tired). So, rather then retype it, here is the link:Techeles Gematria
It is an interesting gematria that I came across in yeshiva. Basically, if you combine some gematrias of the word techeles, and then convert that number (assuming it is in units of amos (~18 inch)) into nano-meters, you get the maximum absorption frequency of light of indigotin (in the visible range), which is the chemical composition of the dye from the murex trunchulus snail (and the indigo plant). Take a look!