Johann Baptist Krebs (1774-1851) was a renowned opera singer, director of operas, freemason, and esoteric writer who wrote under a number of pseudonyms (in particular, J. Kernning and J. Gneiding). He developed a form of letter mysticism composed of the concentrated thinking and feeling of letters through the parts of the body. This practice had its Biblical foundations described in his student Karl Kolb's The Rebirth, the Inner True Life, or How do Humans Become Blessed?, and this technique later influenced the teachings of Karl Weinfurter amongst others.