The [following are the standard] amounts of terumah: [For] a generous person, one [part] in forty. Beis Shammai say: [One part] in thirty; and [for] the average person, [one part] in fifty; and [for] the miserly person, [one part] in sixty. [If] one separated terumah and he took one [part] in sixty, it is terumah, and he need not separate [additional] terumah. [If] he [separated terumah] again to add [to the initial terumah], [what he added] is liable to tithes. [If] he took [one part] in sixty-one, it is terumah but he must separate terumah again according to his custom, by meas-ure, by weight, or by number. R' Yehudah says: Even from that which is not in [its] proximity.

[If] one says to his agent: “Go and separate terumah,” [the agent] should separate terumah in accordance with the mindset of the homeowner. If he does not know the mindset of the homeowner, he should separate terumah using the intermediate [standard], one [part] in fifty. [If] he subtracted ten [parts] or added ten [parts], his terumah is terumah. [But] if he intention-ally added even one [part], his terumah is not terumah.