A newly discovered 1666 manuscript may offer evidence that Galileo Galilei experimented with four-lens telescopes earlier than previously believed, according to research published in the Annals of Science. The manuscript was found by Dr. José María Moreno Madrid, a researcher at the University of Limerick, and was written by Ignacio Muñoz, a Spanish Dominican friar. The document, titled De Tellescopiis Stellarum, describes a four-lens terrestrial telescope, with the phrase "fabricatum a Galilaeo" (manufactured by Galileo), suggesting a direct connection to the famous scientist. Historically, the first four-lens telescopes are believed to have appeared around 1643–45, with their production becoming widespread in the 1640s. If the telescope described in Muñoz’s manuscript was indeed made by Galileo, this would push the earliest known experimentation with such telescopes back to at least 1630 and credit Galileo with the innovation. This would challenge existing historical records and shift our understanding of early telescope development. According to the manuscript, the telescope was presented to Muñoz by Antonio Sebastián de Toledo Molina y Salazar, the viceroy of New Spain and Marquis of Mancera. This was part of a test to evaluate Muñoz’s scientific abilities. At the time, Muñoz had been exiled in Portuguese India for his role in an attempt to establish a new Dominican order in the Philippines. He had written to King Philip IV of Spain, proposing a revolutionary nautical advancement to improve the performance of Spanish fleets. In exchange for royal support, he was promised a return to Spain via the Manila Galleon, which made regular stops in New Spain. The viceroy, suspicious of Muñoz’s scientific claims, ordered him to analyze the telescope in detail. Muñoz described a reverse-tapered four-lens terrestrial telescope with an erecting eyepiece and convex lenses separated by twice their focal lengths. The manuscript also includes detailed diagrams and drawings of the instrument. Galileo had famously claimed he never sold any of his telescopes, and none of the eight surviving telescopes from the first half of the 17th century can be definitively attributed to him. Two telescopes in the Museum of Florence are credited to Galileo, but this attribution is not universally accepted. Moreno suggests that if the four-lens telescope described in Muñoz’s manuscript was indeed made by Galileo, it may have been gifted to the Marquis of Mancera by the Spanish royal family in recognition of his diplomatic achievements. Although there is no further mention of the telescope in Mancera’s correspondence with the Spanish court, the document presents compelling evidence that could reshape our understanding of early modern telescopes and Galileo’s role in their development. Moreno emphasizes that Muñoz, a scholar with a background in math and astronomy, would have been well-equipped to recognize and document such an advanced instrument. Regardless of whether the telescope can be definitively attributed to Galileo, the manuscript adds valuable insight into the technical descriptions of 17th-century telescopes and highlights their status as objects of prestige during that era.