The Collaborative International Dictionary
Perpensity
Perpensity \Per*pen"si*ty\, n. Perpension. [Obs.]
Douglas Harper's Etymology Dictionary
perpensity
"attention," 1704, from Latin perpensus "deliberate," past participle of perpendere "balance carefully" (see perpendicular) + -ity. Noted as obsolete by late 19c.
Wiktionary
perpensity
n. (context obsolete English) perpension