Jan Łasicki was a Polish historian and theologian. He was well-educated and traveled extensively in Western Europe from 1556 to 1581. Around 1557 he converted Calvinism

Calvinism

Calvinism is a Protestant theological system and an approach to the Christian life...

, becoming a follower of the Unity of the Brethren

Unity of the Brethren

The Unity of the Brethren is a Christian denomination whose roots are in the pre-reformation work of priest and philosopher Jan Hus, who was martyred in 1415.-History in Bohemia:...

 after 1567.

His major work is eight-volume Historia de origine et rebus gestis fratrum Bohemicorum. Only one volume survives, which deals with customs and organization of the Brethren and was first published in 1660. His other works include Historia de ingressu Polonorum in Valachiam cum Bogdano (1584) about Polish invasion in Wallachia

Wallachia

Wallachia or Walachia is a historical and geographical region of Romania. It is situated north of the Danube and south of the Southern Carpathians...

. The work was translated into Polish by Władysław Syrokomla in 1855. His 18-page Concerning the gods of Samagitians

Samogitia

Samogitia is one of the five ethnographic regions of Lithuania. It is located in northwestern Lithuania. Its largest city is Šiauliai/Šiaulē. The region has a long and distinct cultural history, reflected in the existence of the Samogitian dialect...

, and other Sarmatians

Sarmatism

"Sarmatism" is a term designating the dominant lifestyle, culture and ideology of the szlachta of the Polish-Lithuanian Commonwealth from the 16th to the 19th centuries. Together with "Golden Liberty," it formed a central aspect of the Commonwealth's culture...

 and false Christians (De diis Samagitarum caeterorumque Sarmatarum et falsorum Christianorum, written ca. 1582 and published in 1615) provides a list of Lithuanian gods and is an important resource in the study of the Lithuanian mythology

Lithuanian mythology

Lithuanian mythology is an example of Baltic mythology, developed by Lithuanians throughout the centuries.-History of scholarship:Surviving information about Baltic paganism in general is very sketchy and incomplete. As with most ancient Indo-European cultures Lithuanian mythology is an example of...

.