I would say a Parrell graph
Yes. Virtually anything can be the theme of an essay, as long as you can find enough information about it to write enough paragraphs to be considered an essay.
<u>Answer</u>:
The grave, where the playwright was buried in 1616, carries the warning: "Good friend, for Jesus' sake forebeare, To digg the dust enclosed heare; Bleste be the man that spares thes stones, And curst be he that moves my bones."