Angelicall Stone
The Angelicall Stone is a concept in alchemy. According to Elias Ashmole the stone was the goal above all goals for the alchemist. In his prologue to the Theatrum Chemicum Britannicum, he states:

Lastly, as touching the Angellicall stone, it is so subtill, saith the aforesaid author, that it can be neither seene, felt, or weighed, but tasted only. The voyce of man (which bears some proportion to these subtill properties) comes short in comparison; nay the air itself is not so penetrable, and yet (Oh mysterious wonder !) a stone, that will lodge in the fire to eternity without being prejudiced.