Constantine the Great

The emperor's body was placed in a golden coffin decorated with imperial purple, transported to Constantinople, and placed in the imperial palace.

An excerpt from the article 18 facts about Constantine the Great

Control of the funeral ceremonies was taken over by Constantine's son, Constantius, who arrived from Antioch.  He ordered that his late father's coffin be moved to the recently completed mausoleum, where the funeral ceremony was continued by Christian clergy. Nevertheless, the funeral ceremony was not strictly Christian; it was mixed in character, with visible pagan influences found in the funerals of earlier Roman emperors.