A description of the first organ construction, called the water organ (hýdraulis), is a matter of interest of not only instrumentologists, but mostly classical philologists. Actually, source texts on the subject had been drafted in Greek and Latin. One of them (lat.) originates from De architectura by Vitruvius Chapter 8, book X (1 BC. – AD 1), another (gr.) – from the work Pneumaticá (1, 42) by Heron of Alexandria (AD 1). Although above mentioned texts concern the same invention, they differ from each other in content, as well as the structure and terminology. Text analysis conducted during translation leads to the conclusion that more detailed and professional is the description by Heron, even though it is chronologically dated as later. It contains ordered instructions for the construction of water organ, which accurately describe all items. The description by Vitruvius lacks this feature and in addition there are inconsistencies in terminology and vague characteristics of some elements of the device. The greatest weakness of the text by the Roman architect is the fact that the reader does not learn what the purpose of water in water organs was. One can conclude that Heron, who operated in Alexandria, had access to the writings of Ctesibius and precise knowledge of the invention. The instrument presented by Vitruvius is a variant of the original device. The consequence of the popular translation of De architectura by Vitruvius and the lack of translation of Pneumaticá by Heron of Alexandria into Polish is a significant confusion in the Polish scientific and popular science literature. Various approaches, interpretations and representations of water organ can be found without any reference to the source. The present article also draws attention to the fact that the most important place in literature, directly informing that the inventor of the instrument was Ctesibius (III BC), is an excerpt from Belopoiicá by Philo of Byzantium (III BC). The second one is a statement by Vitruvius, though it should be noted that it is not included in the famous description of the organs, but in another place. These facts are commonly ignored in the studies and the knowledge of the inventor of the water organs is taken for granted. The readers can find in the present article the original texts and the author’s own translations into Polish. Another issue mentioned is the subject of terminology based on ancient instrument science since it is known that this instrument has not been called organs from the beginning. The paper also attempts to find out when the organs began to function as an instrument in liturgical space of the Catholic Church. On the basis of textual criticism of De musica by Cassiodorus and comparative analysis with other treaties it can be concluded that it happened in the sixth century.