Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 130, § 61

The licensee upon receiving his license shall cause the territory covered thereby to be plainly marked out by monuments, marks or ranges and by stakes or buoys, with the number of his license painted in figures at least two inches in height in a conspicuous place on each of said stakes or buoys or on flags attached thereto, which shall be maintained by him or his transferee during the term of the license or of any renewal thereof. Failure to place or reasonably to maintain the same shall be sufficient cause for revocation of the license.