[noun] + とて [verb た-form] + とて 一 + [counter] + とて + [verb ない-form]
とて means "even" after a noun and "even if" after a verb: whoever it is, or whatever is done, the outcome stays the same. It is literary, found in writing, speeches and set phrases. In conversation you say でも, だって or ても instead.
After a person, とて can also mean "I too", "they too": the person is no exception to what everyone else feels or does.
After a verb, とて usually follows the た-form and means "even if": the action changes nothing. いくら, どんなに or いまさら今さら often come first.
The everyday version of the same sentence uses ても: いまさら今さらこうかい後悔しても、どうにもならない。
These go beyond a single noun or verb.
一 plus a counter plus とて, with a negative verb, means "not a single…". It is the literary twin of いちにち一日も〜~ない.