Anselm Boethius de Boodt:

The Emperor is a lover of stones, and not simply because he hopes thus to increase his dignity and majesty, but through them to raise awareness of the glory of God, the ineffable might of Him who concentrates the beauty of the whole world into such small bodies and in them unites the seeds of all other things in creation.

The alchemist and court physician to Rudolf II, Anselm Boethius de Boodt, wrote about Rudolf II in his work Gemma et lapidum Historia, pubished in 1609.