An emblematic object or personal ornament, such as a skull, used as a reminder of one's mortality.
1995,Klein, Richard,“Introduction”, inCigarettes are sublime, Paperback edition, Durham: Duke University Press, published 1993, ISBN 0-8223-1641-2, OCLC613939086, page 8:
The series of moments [which] the clock records is not only a succession of “nows” but a memento mori diminishing the number of seconds that remain before death.