Are you aware that the LDS Family History Library catalog lists church books for 1860-1939 for the Evangelical church at Lessen? (Lessen was in
Kreis Marienwerder. You can see Lessen on the #42 map in the GEKDR100 series. Order it from
www.genealogyunlimited.com.)
You said he was born in 1848, but not if or when he emigrated. If he did not leave until the 1880s or later, then the church books might show his confirmation around 1862, or perhaps a marriage in the 1870s or so. The latter record would usually give his father's name and place of residence.
You might also find siblings and other
Tesmer relatives in that church.