H. P. Blavatsky

S. The nineteenth letter; numerically, sixty. In Hebrew it is the fifteenth letter, Samech, held as holy because “the sacred name of god is Samech”. Its symbol is a prop, or a pillar, and a phallic egg. In occult geometry it is represented as a circle quadrated by a cross. In the Kabbalah the “divisions of Gan‐Eden or paradise” are similarly divided.

Source: H. P. Blavatsky, The Theosophical Glossary, art. S