∀ {C : Type u₁} [inst : CategoryTheory.Category.{v₁, u₁} C] {J : Type w} [inst_1 : CategoryTheory.Category.{w', w} J]
  {X : C} {K : CategoryTheory.Functor J (CategoryTheory.Under X)}
  (t : CategoryTheory.Limits.Cocone (CategoryTheory.WithInitial.liftFromUnder.obj K)),
  (CategoryTheory.WithInitial.coconeBack✝.obj t).pt = CategoryTheory.Under.mk (t.ι.app CategoryTheory.WithInitial.star)