The story of Mel Mermelstein who took some Holocaust deniers to court and got a California court to take judicial notice of the Holocaust. Specifically, Judge Thomas T. Johnson declared
“This court does take judicial notice of the fact that Jews were gassed to death at Auschwitz Concentration Camp in Poland during the summer of 1944. It is not reasonably subject to dispute. And it is capable of immediate and accurate determination by resort to sources of reasonably indisputable accuracy. It is simply a fact.”https://en.wikipedia.org/wiki/Mel_Mermelstein
This judicial notice had the effect of putting the onus on the other side (i.e. the Holocaust deniers) to prove that the Holocaust did not happen. Considering the mountains of admissible evidence that the Holocaust did happen, this gave the Holocaust deniers an essentially unclimbable mountain to climb if they hoped to win the case. Also, once one court has taken judicial notice of something, other courts are generally quite likely to take the same notice without a huge effort on the party seeking the notice (please keep in mind that IANAL and that a real lawyer would probably find at least a dozen things wrong with this paragraph 🤔).