begun the composition sketch of the first act. During November, however, he set five of Mathilde's poems to music known today as the Wesendonck Lieder. This was an unusual move by Wagner, who almost never set to music poetic texts other than his own. Wagner described two of the songs – "Im Treibhaus" and "Träume" – as "Studies for Tristan und Isolde": "Träume" uses a motif that forms the love duet in Act II of Tristan, while "Im Treibhaus" introduces a theme that later became the prelude to Act III. But Wagner resolved to write Tristan only after he had secured a publishing deal with the Leipzig-based firm Breitkopf & Härtel, in January 1858. From this point on, Wagner finished each act and sent it off for engraving before he started on the next – a remarkable feat given the unprecedented length and complexity of the score. In April 1858 Wagner's wife Minna intercepted a note from Wagner to Mathilde and, despite Wagner's protests that she was putting a "vulgar interpretation" on the note, she accused first Wagner and then Mathilde of unfaithfulness. After enduring much misery, Wagner persuaded Minna, who had a heart condition, to rest at a spa while Otto Wesendonck took Mathilde to Italy. It was during the absence of the two women that Wagner began the composition sketch of the second act of Tristan. However, Minna's return in July 1858 did not clear the air, and on 17 August, Wagner was forced to leave both Minna and Mathilde and move to Venice. Wagner would later describe his last days in Zurich as "a veritable Hell". Minna wrote to Mathilde before departing for Dresden: I must tell you with a bleeding heart that you have succeeded in separating my husband from me after nearly twenty-two years of marriage. May this noble deed contribute to your peace of mind, to your happiness. Wagner finished the second act of Tristan during his eight-month exile in Venice, where he lived in the Palazzo Giustinian. In March 1859, fearing extradition to Saxony, where he was still considered a fugitive, Wagner moved to Lucerne where he composed the last act, completing it in August 1859. Premiere Tristan und Isolde proved to be a difficult opera to stage, and Wagner considered various possibilities for the venue. In 1857 he was invited by a representative of Pedro II, Emperor of Brazil, to stage his