The On-Line Museum and Encyclopedia of Vision Aids.
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Spanish writer, philosopher, engraver and publisher, who published a series of popular manuals on subjects ranging from religion to magic tricks. His writings urged an appreciation of the Fine Arts by the broader public. The famous Cologne-based Minguet Quartet is named after him.
This specific broadsheet from the year 1763 was published in Madrid in a magazine (pamphlet) consisting of approximately 20 pages, consisting mostly of engravings though the last few pages are woodcuts of saints. All these works by Pablo Minguet were from the 1759-1766 period. One copy (missing its front cover) is in the Print Collection of the New York Public Library. This document is now translated into the English Language for the first time below. (Printable PDF file)
Upper Half (With Images)
Demonstration of the eyeglasses that have been invented to save (maintain, conserve) and increase sight
Conservative lens Another conservative Convex lens Half convex Concave lens Half concave Natural sight For tired sight Near sighted
Lower Half (All Text)
Explanation of the use of eyeglasses for all types of people: by Pablo Minguet
Curious readers, knowing the ignorance in which many people live in the way to use eyeglasses, without knowing what would be suitable for each one, I will explain with brevity the way to choose them in order to conserve one’s sight.
Eyeglasses that men commonly use in order to repair sight are the convex, the concave, and the conservative. The convex eyeglasses are thick in the middle of the lenses and thin by the edges and has the ability (likeness) to make things seem big. The concave, on the other hand, thin in the middle and thick on the edges. These make things seem small. These concave eyeglasses and the convex are so opposite from the others (from each other) that if they put them together, being of equal gradations, each one looses its strength and looking with them it will seem conservative. Conservative eyeglasses are those which have equal lenses in the middle and on the edges. These serve to maintain perfect sight and when one tires it lasts a longer time.
The eyeglasses in order to be good have been a fine crystal in order for the conservation of the sight. Because being of crude (rough) glass it is very certain that the sight deteriorates each day. Those of rock crystal they say that they are the best. Those I have not seen.
The person of advanced age that hasn’t used glasses should choose ones that looking at a book they don’t make the letter bigger than that which it is. Looking at it at a distance from where one has to read it because if it is made bigger they therefore have glasses too strong and one wears out their sight. Previously if one had used them defectively but she thought it was working on her part, helping slightly with the eyeglasses of only that degree that it was enough for her to supplement that which she was missing and for that reason, and she is using it, it’s clear that many like seeing more and with the big eyeglass one was getting blinder little by little, finally in the end losing one’s sight. (The essence of this paragraph: if the eyeglasses were too strong they found that it actually didn’t help but did damage to the eyesight).
The person that has the short sight has to use eyeglasses that fit well to their sight and of little increase until they find their compliance (it should be perfectly fit) and not surpass it. But to save it at that degree one is able to do because without feeling it, it (the sight) will go back and it will shorten more.
The person that has unequal sight or variable sight has to look for glasses that have lenses of different grades and these one experiments with, turning the eyeglasses from one side to the other, after one has looked at the letter of a book with them, and one chooses until one finds that fits well to their sight.
The person that because of sickness or blood (congenital) has very bad sight and can’t read takes sunglasses that fits him and orders to be made two thin sheets of tin (metal) the size of the eyeglasses with a row of round openings (little holes) as shown in Fig. 1 or if not some openings they can be a crack or a slice with eight teeth in order to link them and to take them out for cleaning them and you will see by the openings more distinct and black the letter by the small size how you will be able to easily read better the letters.
Some people have put on glasses on a handle or a string (rope) liking more to have them in the hand than putting them on the nose and others value a larger lens putting it on top of the letter and then that which happens is it makes the sight unequal because that style of seeing isn’t for everybody but only for those that do not have more sight than in the one eye.
The glasses being fiddled with or greased up with sweat one takes it off with Tripoli dust (a pinch of snuff) or ash and in order not to streak or dampen the fingers on the flour of the dry ash and with that little that remains on the fingers to rub the lenses and go back and forth with a clean linen.
The eyeglasses that have some color and that saves the sight more is the citron or the turquoise that is the color of the sky and the green. The yellow nor the red are not good. In order to know if the lenses are equal in gradations and clear, one opens the balcony, the window of the room or the lodging (or the Inn).
And in the closet or the darkest place one puts on the wall a white piece of paper that one sees the balcony in front of them and in the controlled distance, having the eyeglasses in the hand, one looks at the degrees or thumbs that they have in focus and one sees if the transparency of the said lenses are equal.
The armature (frame) of the eyeglasses are of many different types from drumsticks (bone), shell and from different metals. And being of metal one is able to put a tin sheet of metal folded with a little bit of tin in order to rest on top of the head under the hat and not to carry them on top of the nose. In Fig. 2 those are of steel in order to have them on the temples. Fig. 3 also they are in order to hang them on the ears in Fig. 4. In Fig. 5 are those of softer steel in order to bring them in the pocket. Those are with a convex lens of different sizes with an armature of wood or of metal and they are for reading, Fig. 6. Ultimately those that are with a concave lens and for those that are for short sight and try to read, Fig. 7.
The eyeglasses of far sight are of two pieces and also in the pocket, Fig. 8 or for the theatre, Fig. 9. The invention consists of a convex lens or half convex which is in front of it and another concave or half concave that is what is put to the eyes but the whole secret it in the convex as she’s good and opens with clarity. One is equipped easily putting its length in its trademark. Also there are the different lenses and tubes of cardboard advising that as long as the eyeglasses are, one sees of the writing if they are good. In the end, there are these other glasses or microscopes with a convex lens for small things to see them bigger, Fig. 10, 11, and 12)
With permission in Madrid in the printing press of the author, 1763, where one will find all of his works very useful for all that one is curious that you will enjoy them.
Engraving of Francisco De Quevedo, 1580-1645, Spanish writer
Engraving of Hieronymus de Praetis Equs, Hubertus van Otteren, circa 1650
Girolamo Capivaccio Paduan professor of Philosophy and Medicine, Poulet's Atlas