Did scholars doubt Belshazzar's existence before 1854?

I was doing some research on people's views on King Belshazzar mentioned in Daniel 5. All the Christian apologists who defend the book of Daniel mention that his existence was disbelieved among the skeptical scholars up until 1854, when an archeological discovery of the Nabonidus cylinders confirmed his existence. That figures, because prior to 1854, all the historians listed Nabonidus as the last King of Babylon. But I was wondering which scholars/historians are actually recorded explicitly stating that Belshazzar didn't exist? Apparently German theologian Ferdinand Hitzig was one of them, websites mention that he said that Belshazzar was 'obviously a figment of the Jewish writer's imagination'. But I went to the source (his book is named Das Buch Daniel, which you can find here https://archive-org.translate.goog/stream/bub_gb_i5JAAAAAcAAJ/bub_gb_i5JAAAAAcAAJ_djvu.txt?_x_tr_sl=de&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=sc) , and when I did a search on the file I couldn't find where he said that, which is why other people say that the claim that Ferdinand made this quote is false. Anyway I just wanted to find out about the group of people who were making this claim.