[Author clarification Saturday October 29, 2016: The original version of this article was subjected to at least one brainless interpretation. Its intention was to refute the claim by Holocaust Deniers that "6 million" was a Holocaust number fabricated at the end of the war that was based on pre-1939 predictions of Jewish catastrophe. Deniers say 6 million was the dominant figure in Jewish culture before the Holocaust regarding a predicted imminent disaster. This article shows that this was not the case as far as quotes in the press are concerned.]
In 1905, the Jewish population of the Russian Empire (including Poland) was counted as 6,060,415. This figure was still being used by American Jewish sources in 1917 (AJC Yearbook, 1916-1917, p. 276). It therefore logically follows that American Jewish organizations seeking aid for their brethren in that region would cite a 6 million figure.
However, the Google News Archive returns these hits for the period 1905-1939:
"Five Million Jews": 42
"Six Million Jews": 44
"Three Million Jews": 57
"Millions of Jews": 1,520
Moreover, stories relating to the imminent starvation, deportation or annihilation of 5 million (not six) can be found here and here and here and here. Similar stories referring to "three million Jews" are here and here. The second article asks for help "so that three million Jews shall not perish from the face of the earth."