Lead coffin no doubt. That's why her remains were in such good condition. And they used glass windows because people were afraid that they'd end up burying someone who wasn't actually dead. They also had coffins that would be attached to a bell above ground, so that if the person in the coffin woke up, they'd be able to alert people. Body snatchers were still active in the late 19th century too.
Abraham Lincoln was the target of an attempted body snatching a decade or so after his death. His captors were going to hold it for ransom and the release of an imprisoned counterfeiter friend of theirs.
Lincoln's body was moved a number of times before his final resting place was ready. Robert Todd Lincoln made damned sure his father would stay put: Abe's casket was surrounded by a steel cage then covered in cement. Before the final interment it was decided to open the coffin, just to make sure it was REALLY him. It was.