Wes Bredenhof recently posted a portion of Guido de Bres' letter to his mother, written shortly before his execution in May of 1567 (http://www.bredenhof.ca/).
This is a very moving and encouraging letter, especially when we consider that de Bres was imprisoned under the worst of conditions (in the sewage of the prison). But as he wrote to his mother, de Bres seems to bask in the assurance of his salvation and the hope of the resurrection. No doubt, this is what Tertullian meant when he said that the that "the blood of the martyrs is the seed of the church."
For background, here's Rev. Bredenhof's discussion of de Bres's martyrdom, followed by the first portion of de Bres' letter to his mother.
Thanks Wes, for posting this wonderful letter!