"The Black Book of Carmarthen," written in Welsh and dating back to 1250, contains texts from the ninth through 12th centuries, including some of the earliest references to the legendary King Arthur and the wizard Merlin.

"It's easy to think we know all we can know about a manuscript like the 'Black Book,' but to see these ghosts from the past brought back to life in front of our eyes has been incredibly exciting," said Myriah Williams, a doctoral student at the University of Cambridge, according to Live Science. "The drawings and verse that we're in the process of recovering demonstrate the value of giving these books another look."

The founder of the National Library of Wales, Sir John Williams, purchased the book in 1904. Williams and Paul Russell, a professor at Cambridge's department of Anglo-Saxon, Norse and Celtic (ASNC), only recently examined the book, which measures 6.7 by 5 inches.

"The margins of manuscripts often contain medieval and early modern reactions to the text, and these can cast light on what our ancestors thought about what they were reading," Williams said, according to Live Science. "The 'Black Book' was particularly heavily annotated before the end of the 16th century."

Jaspar Gryffyth, a 16th-century owner of the book who copied his name in Hebrew onto the book, might have taken it upon himself to "clean up" the manuscript's doodles. "He fits the time frame for the erasures, which we know would have been in the late 16th century, but we can only speculate that he might have been the one to take it upon himself to 'cleanse' the manuscript," Williams told Live Science in an email.

With UV light and photo-editing software, Williams and Russell caught glimpses of some of the erased markings. Page fol. 39v includes ghostly faces and a line of text dating back to the 14th or 15th century. The next page, fol. 40v, a full verse, possibly dating to the 13th century, was revealed. "There is one more drawing so far that we are still working on," Williams said, according to Live Science.

"What we have discovered may only be the tip of the iceberg in terms of what can be discovered as imaging techniques are enhanced," Russell said according to Live Science. "The manuscript is extremely valuable and incredibly important - yet there may still be so much we don't know about it."