Who was the first to prove that for every set $X$, there exists a set of all sets hereditarily strictly subnumerous to $X$, in ZF alone (i.e.; without choice)?
Where $S$ is hereditarily strictly subnumerous to $|X|$ means that: $$\forall s \in \text {trcl}(\{S\})(|s| < |X|)$$; where $|Y|$ is the Scott's cardinality of $Y$; and $$\text {trcl}(S)= \bigcup\big{\{}S, \ \bigcup S \ , \ \bigcup\bigcup S \ , \bigcup \bigcup\bigcup S, ... \big{\}}$$