As Figulus stated in a recent answer:
But passive infinitives are not the only infinitives which lack a gerund. Posse and esse also lack a gerund, and that brings to my mind the neo-Latin expression, A posse ad esse (from being able to merely being)
I'd never noticed this before—but certainly I can't recall ever seeing a gerund for these verbs.
I know esse had some of its missing forms filled in by later authors. For example, since it didn't have a present participle in Classical times, essens and ēns were created by analogy and appeared sporadically in later authors.
Did similar gerundive forms ever appear? That is, did any sort of gerundive for esse or posse ever catch on in post-Classical Latin and see widespread use?