Thinking about the depth of space and visually explaining it are two different things--vast numbers and the deepest depths, all colliding with the imagination, which really has a hard time keeping up with it all.
This beautiful engraving appeared in Amedee Guillemin's Le Ciel: notions d'astronomie a l'usage des gens du monde et de la jeunesse, which was published by Librairie de L. Hachette and Company, and printed in 1865 (the images from which are available here). Guillemin (1826-1893) was a social/culture writer who became a very respected science journalist/writer, becoming very popular with works in physics, technology, astronomy and general science, many lavishly illustrated.
There are many striking images in this book, The Sky/the Heavens..., but I've chosen this one because it has a certain deep depth to it, and relays a complexity and distinctness to something that is generally imaged as being less so, being a massive star cluster and all. Unlike many of his other books, the great illustrations here are the small text images, some only 25% of the page, and in most cases rendered sparingly, and with a real feel of "difference" to them (at least so to me).
The "Amas du Toucan", known now more familiarly as 47 Toucanae or 47 Tuc (NGC 104), is a bright element in the southern sky, a huge cluster 120 light years wide and 16,700 light years from Earth, visible to the naked eye in the constellation Toucan (created by Petrus Plancius in 1598 or so). And here it is, in a little 9x8 cm engraving with hundreds of white points as stars, made after an engraving of Sir William Herschel (1738-1822, a German-born English astronomer who--with his sister Caroline and brother John--spent decades observing and recording stars, double stars, clusters and nebulae).
47 Tuc was first catalogued as not-a-star by Abbe Nicolas Louis de Lacaille (1713-1762), a French astronomer who found it too be too fuzzy to be a single star, and who produced a 10,000 (Southern) star catalog, Coelum Australe Stelliferum, which was published in 1762, and which also introduced 14 new constellations. 47 Tuc made another quick appearance in the great Catalogue des Nébuleuses et des Amas d'Étoiles ("Catalogue of Nebulae and Star Clusters"), a superb and meticulous work by Charles Messier, and published in 1771.
But distances and depths such as we know them now were not-conceivable at this point for Guillemin--and really would be for another 60 years or so. At this point, and for some time to come, the Milky Way was considered to be the entirety of the universe. The business of galaxies being outside of the Milky Way is a relatively recent development, determined so by Harlow Shapley in 1924, expanding the size of the universe ten-fold to 300,000 light years; this was blown up a quite a bit by Edwin Hubble in '24 to 900,000 light years, and then five years later in one of his most famous papers Hubble blew the figure up a lot, expanding the universe to 280 million light years. Walter Baade and others added to the figure in the 1950's (4 billion light years or so), and during the 1960's-1990's the figure expanded to 25-30 billion light years, finding its way to 94 billion light years in 2006.
I would imagine that the concept of galaxies outside of our own, and that the universe was vastly larger than we thought, and that the potential for there being new/unforeseen discoveries was great, that in 1924/1929 it may have seemed somewhat like Galileo suddenly seeing an order of magnitude more stars than had ever been seen before by the naked eye...that the sky which had basically been unchanged in appearance to humans for thousands of years really wasn't what people thought it was. Perhaps it was like the Two Dimensional beings in Flatland trying to comprehend the first appearance of a Three Dimensional entity. Or of course the realization could have been like when Sandy Cheeks came to the shocking epiphany in an episode of the Immortal Sponge Bob Square Pants that the titanic battle she had been waging and ostensibly won with an Alaskan Bull Worm was just her fighting with the tip of the beast's tongue--oh. Oh my. Something along those orders. Deep depth.
The Guillemin work is simply a lovely and elegant thing--one of many accomplishments in a beautiful and relatively simple book.