Upon recovering from a life-threatening illness, Donne in 1623 wrote Devotions upon Emergent Occasions, the most enduring of his prose works. Each of its 23 devotions consists of a meditation, an expostulation, and a prayer, all occasioned by some event in Donne's illness, such as the arrival of the king's personal physician or the application of pigeons to draw vapours from Donne's head. 

"John Donne", Britannica