Billed as “one of the greatest rarities of English literature”, a signed copy of William Butler Yeats’s first play, Mosada, is on display this weekend for the first time since 1956 – and its £125,000 price tag is all thanks to a message from beyond the grave. London dealer Peter Harrington today has the book on sale at the Boston International Antiquarian Book Fair. It was last displayed at Trinity College Dublin 67 years ago. Written in 1886, when Yeats was just 21, Mosada is a short verse play that had a print run of 100. Only 21 are thought to have survived, nine signed. This one has Yeats’s signature, but also a problematic dedication. It was signed to what for many years was thought to be a “Mrs Zena Powell, from her friend, the author”. No such person could be found in any records when it came to establishing the provenance of the copy, so Harrington embarked on a bit of detective work before acquiring it. Yeats scholar Professor Warwick Gould discovered that the inscription was actually to Zena Vowell and that there was a reference to her in a report of a séance almost a century ago. Gould told the Observer that once he worked out that the surname was Vowell “a vast baggage of useless speculation fell away”. He said: “I then searched for Zena Vowell in Google Books. Up came a sole page in Polish with some English names swimming in a text I could not read. A rough translation confirmed that at a London séance in 1924, witnessed by the spiritualist Herbert Bradley, the ‘ghost’ of a Zena Vowell had spoken to the medium Hester Travers Smith of their jaunt to Howth, Co Dublin, eight years before her death or transfiguration.” Bradley provided an account of the séance in his 1924 book Towards the Stars, which was the only reference that could be found to Zena. Gould said: “I am no believer, but that afternoon I held Bradley’s Towards the Stars in the British Library, and read the full proceedings of the séance. After that I found Zena Vowell in the Irish census.” Zena – or Thomasina – Vowell is thought to have been born in Waterford in 1831 and in the séance it was established she had known the medium. Travers Smith was the daughter of the Irish poet and critic Edward Dowden, who had helped Yeats’s father, John Butler Yeats, publish Mosada by gathering subscribers. Zena Vowell is now thought to have been one of them. With this direct link to Yeats, the book – which was last on sale in 1962 at auction – has earned itself the £125,000 valuation. Philip Errington, a senior specialist at Peter Harrington, said: “An inscribed copy of Mosada will always have a commercial value. “Accurately identifying the recipient and working out why she received a copy is a significant detail and gives a better history of this copy. “It’s exciting, with this particular book, to suggest it’s a copy inscribed to a subscriber. “Some copies of books have their own stories to discover. This one responded to close detective scrutiny and it’s always satisfying when that happens. “I’ve been in the book world for almost a quarter of a century, and this is certainly one of the strangest uses of source material. It’s wonderfully spooky that the report of a voice beyond the grave helped.”