The play Thamos, König in Ägypten, by Tobias Philipp von Gebler, had its Viennese premiere in the Kärntnertortheater on 4 Apr 1774, the Monday after Easter, with choruses by Mozart (Dokumente, 133–34). The history of Mozart’s incidental music for Thamos (K. 345) is complicated by revisions and additions for later productions. However, it seems relatively certain that early versions of choruses 1 and 6 from K. 345 (“Schon weichet dir, Sonne” and “Gottheit”) were performed in the Viennese production of 1774.
The essay from which this passage is drawn is not a review of Thamos or of the performances in Vienna in 1774, but rather a short essay on the place of theater in an enlightened state. The author touches on the play itself only on p. 96, writing: “Wir werden von gegenwärtigem Stücke keinen Auszug mittheilen, weil wir wünschen, daß es unsere Leser selbst sehen oder doch lesen mögen." (“We will not discuss the present play, because we wish that our readers themselves may see it or at least read it.”) Mozart's choruses are praised in the last sentence of the essay.
The journal title given above is taken from the title page of the volume in which this passage appears. The journal is also known simply as Auszüge aus den besten literarischen Journalen Europens, the title under which this volume appears in Google Books. The journal was issued in 1773 and 1774 by the Viennese theologian and writer Franz von Paula Rosalino (1736–1793).