What is the Regius Poem?

Sometimes called the Halliwell Document, it is, loosely speaking, the oldest of the "Manuscript Constitutions" of Freemasonry. Dated approximately A.D. 1390, it is in old Chaucerian English, difficult to read without a translation. It is preserved in the British Museum.
It is not, accurately speaking, a "Constitution," although it has within it much that is found in
manuscripts. It is more a document about Masonry than for Masons. It is discursive, rambling, wordy and parts of it are copies of contemporary documents, notably "Urbanitatis" and "Instructions to a Parish Priest." Within the Regius, thirty-eight lines are devoted to "The Four Crowned Martyrs," who are not referred to in any of the manuscript Constitutions.
The book is approximately four by five and onehalf inches, the pages fine vellum, the letters in red and what was probably once black but is now a rather drab greenish brown color.
Its most curious feature is that it is written in verse, which is why it is often called the Regius Poem, although it is much more doggerel than poetry.
It is important to Masonic students for many reasons; to the average Mason its most salient feature may be that it ends with what are, so far as is known, the oldest words in the Masonic ritual (see "Why do we use "So mote it be" instead of "Amen"?).