As to the character and quality of the crystal to be used, Abbot Tritheim, the master of the famous Cornelius Agrippa, says:[276]
Procure of a lapidary a good, clear, pellucid crystal of the bigness of a small orange,—i.e., about one inch and a half in diameter; let it be globular, or round each way alike; then you have got this crystal fair and clear, without any clouds or specks. Get a small plate of pure gold to encompass the crystal round one-half; let this be fitted on an ivory or ebony pedestal. Let there be engraved a circle round the crystal; afterwards the name: Tetragrammaton. On the other side of the plate let there be engraved, Michael, Gabriel, Uriel, Raphael, which are the four principal angels ruling over the Sun, Moon, Venus, and Mercury.
The four letters constituting the Tetragrammaton are the Hebrew characters yôdh, hê, wâw and hê, יהוה. As this divine name was regarded in later Judaism as too sacred to be pronounced, the word lord, adonai, was substituted for it in the reading of the Scriptures. For this reason, when the vowel signs were added to the text to indicate the traditional pronunciation, the consonants Yhwh were provided with the vowels of adonai and the name was therefore read Jehovah by Christian scholars.
The Persian poet Jâmi writes thus of a magic mirror in the poem “Salamân and Absal”:[277]
Then from his secret Art the Sage Vizyr
A Magic Mirror made; a Mirror like
The bosom of All-wise Intelligence,
Reflecting in its mystic compass all
Within the sev’nfold volume of the World
Involved; and looking in that Mirror’s face