to reckon without one's host

Webster's Dictionary (GCIDE)

1.To make an enumeration or computation; to engage in numbering or computing. --Shak. [1913 Webster]

2.To come to an accounting; to make up accounts; to settle; to examine and strike the balance of debt and credit; to adjust relations of desert or penalty. [1913 Webster]

"Parfay," sayst thou, "sometime he reckon shall."— Chaucer.[1913 Webster]

To reckon for, to answer for; to pay the account for. "If they fail in their bounden duty, they shall reckon for it one day." --Bp. Sanderson.

To reckon on To reckon upon, to count or depend on; to include as a factor within one's considerations.

To reckon with, (a) to settle accounts or claims with; -- used literally or figuratively. (b) to include as a factor in one's plans or calculations; to anticipate. (c) to deal with; to handle; as, I have to reckon with raising three children as well as doing my job. [1913 Webster +PJC]

After a long time the lord of those servants cometh, and reckoneth with them.— Matt. xxv. 19.[1913 Webster]

To reckon without one's host, to ignore in a calculation or arrangement the person whose assent is essential; hence, to reckon erroneously. [1913 Webster]