Vienna, Austria—"Please forgive me for what I've done, I could not resist love" -- these are the final dramatic words of Baroness Mary Vetsera, whose farewell letters were discovered in a bank vault in Vienna 126 years after she famously committed suicide with Crown Prince Rudolf of Austria, experts announced Friday.

Hailing the find as "sensational", the Austrian National Library (ONB) said bank employees had stumbled across the precious documents during a clear-out of the archives.

They had been there since 1926, according to the library.

"An unknown person deposited a leather-bound folder containing numerous personal documents, letters and photographs of the Vetsera family, including the farewell letters of Mary Vetsera from 1889," the ONB said in a statement.

"Dear Mother/ Please forgive me for what I've done/ I could not resist love/ In accordance with Him, I want to be buried next to Him in the Cemetery of Alland/ I am happier in death than life," the letter to Helen Vetsera read.

The ONB said it hoped the discovery would help shed light on one of the world's great romances, which has inspired numerous movies, novels, ballets and plays.

The bodies of Mary Vetsera, two months shy of turning 18, and the 30-year-old crown prince were discovered in January 1889 at a hunting lodge in the Viennese woods near the town of Mayerling.

The exact circumstances of their suicide-pact, commonly referred to as the "Mayerling incident", still remain unclear.

The prince is thought to have shot his lover before turning the gun on himself.

Their deaths sparked international headlines and became a source of speculation.

With the exception of a farewell letter from Rudolf to his wife, Stephanie, no other original documents related to the incident were believed to have survived.

"Until now it had been assumed that the letters had been destroyed after the mother's death," the ONB said.

Scientific research on the letters would begin in August, it added.

The letters, addressed to the baroness's mother, sister and brother, had been kept inside a closed envelope sealed with the crown prince's insignia.

The historical documents will go on public display at the library in 2016, as part of celebrations to mark the centenary of Emperor Franz Joseph's death.