The following description was prepared by William Gross:
Kabbalistic diagrams resembling Porphyrian trees have been known at least since the sixteenth century as “Ilanot” [Heb. pl. Arborae; sing. "Ilan"]. [First such reference known to me is in the work of Guillaume Postel, who refers to "Ilanoth" as a genre of rabbinic literature.] Ilanot constitute visual representations of kabbalistic cosmologies from the relatively simpler forms of the thirteenth century to the far more complex and ramified systems in Lurianic Kabbalah from the sixteenth century onward. The increasing complexity of cosmic trees between the thirteenth and eighteenth centuries directly reflects the exponential ramification of kabbalistic theosophy that took place over those centuries. Given the overwhelmingly visio-spacial conceptions of the divine in its evolutionary “becoming” in these mystical traditions, Ilanot could serve as cosmic maps. This divine cartography aspired to capture the synchronic interrelations between the various facets of the godhead and creation as well as their diachronic, evolving emergence.
What’s an Ilan? Any synoptic diagrammatic presentation of kabbalistic cosmology. The basic graphical forms could range from the arboreal to the boldly anthropomorphic. Lurianic Ilanot, in their lengthy and complex presentations, often feature both, as well as spreadsheet-like tables. The iconic decadal tree is an Ilan, as is the intricately Baroque Hammerschlag Ilan. Diagrams expressing particular concepts within a larger framework, such as the illustrations that frequently accompany certain cosmogonic discussions in the Lurianic corpus, would doubtfully have been called ilanot by anyone. However simple or complex the pictorial-diagrammatic features of an Ilan, extensive textual material is frequently embedded in and around the geometrical forms. The texts may be paraphrastic chapter headings, original compositions, or the study notes of a student. Their connection to the pictorial features alongside which they appear is usually clear, with the text providing a verbal key to the quality or process depicted graphically. That said, in complex Ilanot, simple keying gives way to more complex and even inscrutable connections. Indeed, these manuscripts demand to be treated as “integrated systems of communication” that raise “questions about how verbal and visual patterns of meaning were constructed, combined, and modified.”
While amulets indicate a popular mystic belief, there exists a strong esoteric and intellectual trend of mysticism in Jewish tradition as well, called the kabbalah. As an aid in understanding the "spheres' and relationships of the mystical world of the kabbalah, some kabbalah scholars would write a long scroll with a visual rendering of this order. The earliest such scrolls are apparently of the 16th century. The first printed version of such a scroll, according to the tradition of Ha’ari, one of the greatest kabbalists, was produced in Warsaw in 1864. This exhibited manuscript scroll is the model on which that printing was based, even including the same censor's comments that appear on the printed version. The printed scroll is also presented in this exhibit next to this manuscript version. In this MSS version the censor's approval is dated 1864, the year of the printing. Approval was needed on the scroll before it could be published. The scroll is comprised of 12 sections glued together. It is possible that this original scroll from which the print of 1864 was copied is of an earlier date in the 19th century. The scroll is written on 12 sections of paper glued together.