Abbé Jean-François-Victor Bieil.
According to Gérard de Sède, Saunière travelled to Paris in 1892. He allegedly went their to seek help decoding a number of parchments he found in his church. He is said to have spoken to Abbé Jean-François-Victor Bieil who was the Director of Saint-Sulpice at the time. Bieil was also the uncle of Emile Hoffet, who is said to have eventually decoded the documents.
In 1903 Bishop LaCroix of Tarentaise published a memoir about Bieil that may be downloaded through this link.