We know that the Library of Alexandria had pretensions to store all the universal knowledge of the time, but, how many volumes had actually?
This dream of storing all the knowledge of time dazzles every so often to men, at least some dreamers. In Alexandria it is sought to collect "books of all peoples on the earth" and might think that they needed to collect 500,000 volumes.
The various sources of very different times, although drinking each from other, give us very different figures.
We read in the Letter of Aristeas, 9 et seq., work of the third century BC and first text preserved in which the Library of Alexandria is quoted, famous mainly because it comments the translation of the Pentateuch into Greek for the Library:
Demetrius of Phalerum, the president of the king's library, received vast sums of money, for the purpose of collecting together, as far as he possibly could, all the books in the world. By means of purchase and transcription, he carried out, to the best of his ability, the purpose of the king. On one occasion when I was present he was asked, How many thousand books are there in the library? and he replied, 'More than two hundred thousand, O king, and I shall make endeavour in the immediate future to gather together the remainder also, so that the total of five hundred thousand may be reached. I am told that the laws of the Jews are worth transcribing and deserve a place in your library.' 'What is to prevent you from doing this?' replied the king. 'Everything that is necessary has been placed at your disposal.' 'They need to be translated,' answered Demetrius, 'for in the country of the Jews they use a peculiar alphabet (just as the Egyptians, too, have a special form of letters) and speak a peculiar dialect. They are supposed to use the Syriac tongue, but this is not the case; their language is quite different.' And the king when he understood all the facts of the case ordered a letter to be written to the Jewish High Priest that his purpose (which has already been described) might be accomplished. (R.H. Charles-Editor. Oxford: The Clarendon Press, 1913)
And so we read it also in Josephus, Jewish Antiquities, 12. 2
Demetrius Phalerius, who was library keeper to the king, was now endeavoring, if it were possible, to gather together all the books that were in the habitable earth, and buying whatsoever was any where valuable, or agreeable to the king's inclination, (who was very earnestly set upon collecting of books,) to which inclination of his Demetrius was zealously subservient. And when once Ptolemy asked him how many ten thousands of books he had collected, he replied, that he had already about twenty times ten thousand; but that, in a little time, he should have fifty times ten thousand. But be said he had been informed that there were many books of laws among the Jews worthy of inquiring after, and worthy of the king's library, but which, being written in characters and in a dialect of their own, will cause no small pains in getting them translated into the Greek tongue; that the character in which they are written seems to be like to that which is the proper character of the Syrians, and that its sound, when pronounced, is like theirs also; and that this sound appears to be peculiar to themselves. Wherefore he said that nothing hindered why they might not get those books to be translated also; for while nothing is wanting that is necessary for that purpose, we may have their books also in this library. So the king thought that Demetrius was very zealous to procure him abundance of books, and that he suggested what was exceeding proper for him to do; and therefore he wrote to the Jewish high priest, that he should act accordingly. ( Flavius Josephus, Antiquities of the Jews . William Whiston, A.M., Ed. )
Maybe collecting ideas of Demetrius, it is pretended to create a universal library, but most of the books were Greek, and it will occupied about 500,000 volumes of all subjects. In any case the actual amount should have been so impressive that the Ancients have given fantastic figures of many thousands of volumes, but it is necessary to keep in mind that a work had several volumes or papyrus rolls, and each roll can be equivalent to current pages 60-70 and its length is usually between 6 and 10 meters, but it can be much higher.
These figures should be taken with many reservations because at first they seem impossible.
We have already seen in the above letter of Aristeas, 9-10, that it is said that in the time of Demetrios of Falera the Library had 200,000 volumes, in the early second century it would reach 500,000 and as Gelius says it have reached 700,000 volumes, although we have to take in mind that a work had multiple volumes or rolls of paper.
Gellius says in Noctes Atticae VII, 17.3:
At a later time an enormous quantity of books, nearly seven hundred thousand volumes, was either acquired or written in Egypt under the kings known as Ptolemies;
Ingens postea numerus librorum in Aegypto ab Ptolemaeis regibus vel conquisitus vel confectus est ad milia ferme voluminum septingenta;
Ammianus speaks also about 700,000 volumes. But in some manuscripts of Gellius it is said 70,000 but not 700,000 volumes. Interestingly the 200,000 of the letter of Aristeas plus 500,000 of target of Philadelphus are the 700,000 volumes of Gellius.
Seneca says that at in Alexandria they are burned 40,000 books, but as we shall see later, these books were not really the bibliographic collection of the library. He says just on a text in which he criticizes the ostentation of rich Roman citizens who store numerous volumes, which never they read, for appear they are cults. This behavior is not out of some contemporary .. He says in De tranquillitate animi, 9, 4:
What is the use of having countless books and libraries, whose titles their owners can scarcely read through in a whole lifetime? The learner is, not instructed, but burdened by the mass of them, and it is much better to surrender yourself to a few authors than to wander through many. Forty thousand books were burned\b at Alexandria; let someone else praise this library as the most noble monument to the wealth of kings, as did Titus Livius, who says\c that it was the most distinguished achievement of the good taste and solicitude of kings. There was no "good taste" or "solicitude" about it, but only learned luxury – nay, not even "learned," since they had collected the books, not for the sake of learning. But to make a show, just as many who lack even a child's knowledge of letters use books, not as the tools of learning, but as decorations for the diningroom. Therefore, let just as many books be acquired as are enough, but not for mere show (Translated by John W. Basore. www.stoics.com)
Quo innumerabiles libros et bibliothecas, quarum dominus uix tota uita indices perlegit? Onerat discentem turba, non instruit, multoque satius est paucis te auctoribus tradere quam errare per multos. 5 Quadraginta milia librorum Alexandriae arserunt. Pulcherrimum regiae opulentiae monumentum alius laudauerit, sicut et Liuius, qui elegantiae regum curaeque egregium id opus ait fuisse. Non fuit elegantia illud aut cura, sed studiosa luxuria, immo ne studiosa quidem, quoniam non in studium, sed in spectaculum comparauerant, sicut plerisque ignaris etiam puerilium litterarum libri non studiorum instrumenta, sed cenationum ornamenta sunt. Paretur itaque librorum quantum satis sit, nihil in apparatum.
Orosius, who seems to have drunk in Livy, speaking about the war of Alexandria, said that 40,000 books were burned, though some manuscripts give 400.
St. Isidore speaks about just 70,000 rolls.
The bishop Epiphanius tells us that Serapeion library, called "daughter" would have 54,800 volumes in his "Weights and Measures" in chap. 9 (52c):
"There are already fifty-four thousand eight hundred books, more or less; but we have heard that there is a great multitude in the world, among the Cushites, the Indians, the Persians, the Elamites, the Babylonians, the Assyrians, and the Chaldeans, and among the Romans, the Phoenicians, the Syrians, and the Romans in Greece"—-at that time called not Romans but Latins.
Juan Tzetzes, Byzantine scholar and writer, who lived between approximately 1110 and 1180, in his Prolegomena to Aristophanes says that the museum had collected 400,000 "mixed books" (symmigeis) and 90,000 "non-mixed" (amygeis), making difficult to interpret what “mixed” and “no-mixed” means, perhaps it refers to a roll with a single work and rolls with several works. Moreover Tsetzes is based on the letter of Aristeas, and in any case, he should express the idea that the library had a huge number of papyrus rolls.
Ibn-al Qifti (lived ca. 1172-1248) Arab historian, author of a History of philosophers, also speaks of 54,000 rolls.
It seems that it is mixing different aspects: the myth that the library intended to store a copy of every book in the world and therefore its goal of reach 500,000 volumes, the huge amount that it actually had, which were burned in the famous fire because of the war in Alexandria.
Modern authors have attempted to calculate more rationality really possible existing volumes.
Hipólito Escolar Sobrino, in his work The Library of Alexandria (Madrid: Gredos, 2001), p. 136-138, estimates that it could have some 50,000 volumes or rolls and that would equate to about 12,500 current books.
There are other even less cheerful calculations. So considering that the 24 songs of Homer's Odyssey need 24 rolls and now they fit into a modern volume and admitting that Alexandrian Library had 500,000 papyrus rolls, we would have about 20,000 modern books. But if it ad 50,000 rolls, it would have around 2,000 modern books, inadequate number for the mythical assessment that it enjoys. The “bibliotheke” with its 500,000 papyrus scrolls was therefore much smaller than one might have imagined.
In any case, they dreamed to collect all the books on the world and translate them into Greek, because not only a merely collector intent encouraged them , but also the knowledge of men and cultures of the world. But does not this also the dream of contemporary projects as "Google Books", for example? Do not seek other grandiose projects like Wikipedia to build the actually universal encyclopedia?