ponderable

adj

1. Having a detectable amount of matter; having a measurable mass.

   “[T]he imponderability of heat did not appear to the philosophers of the eighteenth century to be a sufficient reason for excluding it from the list of chemical elements; and... there was... doubt... whether caloric was ponderable or not.”

2. Worthy of note; significant, interesting.
3. (rare)Heavy; ponderous.

   “The very mother's head you swore by in the dock is a heavier head, crowned with ponderable hair.”