In this article from Scribner's Monthly Magazine Henry Hatton, writing under the pseudonym of an 'Ex-Conjurer' explains in detail the two-person code system used by Robert Heller. It consists of five different parts based on different methodologies to make detection by the audience impossible.
1st edition 1880, PDF 10 pages.
word count: 3444 which is equivalent to 13 standard pages of text
