Master engineer Abu Rayhan al-Biruni was a Persian scholar and old friend of the Holy Roman Emperor Otto I. He is mentioned in one of the letters in Wolfenstein: The Old Blood.
King Otto I commissioned him to create large reinforced chains which could withstand jerking and pulling by a force equal to that of three hundred horses. The chains' purpose was to keeping the monsters created by Otto's scholars about what he hadn't told al-Biruni to keep the existence of the creatures as the secret. Al-Biruni's ironworkers and staff were baffled and insist that such large chains had no practical use. The Master engineer itself was curious what was the real purpose of the reinforced chains, about what he enquired King Otto in the letter to him.
The letter to King Otto was written both in 10th century Persian and Old High German and before events of The Old Blood was translated into modern German by Gottfried Winkler for Helga von Schabbs.