Interesting video but I dispute his 19th Century limit on cursive cross-writing.
Several famous "Beat" authors including
Jack Kerouac and William S. Burroughs, when writing in notebooks instead of using typewriters, played with cross writing as their notebooks became filled. A lesser known collaborative novel entitled "
And the Hippos Were Boiled in Their Tanks" published in book form in 2008 had both authors writing over each other in manuscript including cursive over collage from newspaper accounts of the subject of the novel.
Author and English professor
Samuel R. Delany featured cross-writing throughout his epic 1975 SF novel "
Dhalgren". Mysterious stranger Kid receives a notebook from his (future) lover filled with prose but only on one side of each page. Deciding to write poetry describing his surroundings, Kid covers blank sections of the notebook with cursive writing, fitting it where he can including writing over previous text.
This cross-writing and cross-fertilization of ideas becomes so central to Delany's notions of communication and discourse that excepts from Kid's notebook appear in an Appendix titled Anathemata. This final chapter displays text versions of cursive writing two and even three levels deep spanning different times in the long novel including (possibly) before "Dhalgren" begins and even after the action ends due to the time digression inherent in cross-writing (new text written across and beside previous text).