From the 1920 book Manual of Library Economy, a description of an early hipster PDA:

The Card Diary.–A useful little card index is one which
may go on a desk, and is guided with the days of the week, and
has such other guides as “This Week,” “To-day,” “Next Week,”
“Miscellaneous matters,” etc., which serves as a reminder to its
user. Behind the appropriate guide are filed cards referring to
the matters which are to be dealt with at the time indicated.
These card-diaries are commonly known as “ticklers,” and can
be a most effective aid to methodical administration.

The next handy tip is how to make a card catalog to help you organize your office supplies. Really.