1623, William Shakespeare, Troilus and Cressida, First Folio, IV.7:faith and troth, Strain'd purely from all hollow bias drawing: Bids thee with most diuine integritie, From heart of very heart, great Hector welcome.
(now rare) Without physical adulterants; refinedly, with no admixture. from 16th c.
1823, Samuel Taylor Coleridge, Table Talk:By some means or other the water flows purely, and separated from the filth, in a deeper and narrower course on one side of the rock, and the refuse of the dirt and troubled water goes off on the other in a broader current ....