Talmud (Rodkinson Edition) — Book 2…
“ If the Erub rolls (or is moved) out of the limit of the Sabbath distance? If the time when it took place is doubtful? If a clean and unclean loaf were before a man, and he was told to make an Erub with the clean one, but did not know which was which? Said R. Na'hman to Rabha: If thou wilt measure a whole kur of salt and present me with it, I shall tell thee the answer. A man may make his Erub conditional. If one of the two sages had been the man's teacher, he must go to meet his teacher. It frequently happens that a man has a greater fondness for his colleague than for his teacher. ”
