On 23 July 1914, the Austro-Hungarian Ambassador to Serbia Baron Wladimir Giesl (pictured) sent a coded telegram to the Austro-Hungarian Minister of Foreign Affairs Leopold Count Berchtold. In his telegram, Giesl informs Berchtold on the upcoming delivery of the Austro-Hungarian ultimatum to Serbia.
Baron von Giesl to Count Berchtold. Belgrade, 23 July 1914.
I will deliver the note to Minister Pacu [note: a Serbian cabinet minister] at 16:30 today. My hint, that perhaps [Serbian Prime] Minister [Nikola] Pasic ought to be informed, was rejected as superfluous on the grounds that Minister Pacu had yesterday been appointed by decree as representative of the premier and of the Minister of Foreign Affairs.
Source: 1919 Austro-Hungarian Red Book, with minor edits.