The Ordinarium Sanctae Romanae Ecclesiae written by Jacobi Gaytani, placed a strict limit on the amount of candidates a cardinal could involve.
Gaytani (a participant in five papal conclaves between 1305 and 1352) included no restriction on the number of candidates a cardinal could include on his ballot during a scrutiny, but advised not to choose too many "for decency and expediency". 
