The stuff called myrrh.

Myrrh is mine, its bitter perfume
Breathes of life of gathering gloom
Sorrowing, sighing, bleeding, dying
Sealed in the stone-cold tomb

From the American carol We three Kings of Orient written in 1857 by the Rev. John Henry Hopkins.

Myrrh is a highly aromatic oleoresin (a natural blend of essential oils and resin) produced by a number of small, thorny tree species, includingCommiphora myrrha, which grow in the dry, stony soils of the Middle East.

Best seen through the looking glass.