The Zoso symbol chosen by Jimmy Page as his symbol for the 4th album cover was originally written down by a 16th century hermeticist J. Cardan in a classical 1557 work Ars Magica Arteficii. This book is now out of print and highly sought after, but no doubt Page had access to a copy when Jimmy owned his bookshop. However, you can see the symbol in the book "Dictionary of Occult, Hermetic and Alchemical Sigils" by Fred Gettings, published in 1982 by Routledge & Kegan Paul, ISBN 0-7100-0095-2. This book also tends to go wandering from libraries due to interest from folk practising witchcraft

In the section "Planetary Symbols" on page 201, under Sigils, for planet Saturn Cardan's 1557 symbol is virtually identical to the Zoso symbol above (and nothing else in the occult dictionary is even vaguely similar).