Definition of "accessional"

Again, whereas men affirm they perceive an addition of ponderosity in dead bodies, comparing them usually unto blocks and stones, whensoever they lift or carry them; this accessional preponderancy is rather in appearance than reality.

1650, Thomas Browne, Pseudodoxia Epidemica: […], 2nd edition, London: […] A[braham] Miller, for Edw[ard] Dod and Nath[aniel] Ekins, […]