It took me some searching, but it seems this is the best way to run a single cron command, in this case the scheduler cron job to publish and depublish content:
* * * * * drush --root=$HOME/httpdocs eval "scheduler_cron();"
It’s safe to run this every minute and leave the normal cron job to run every hour:
0 * * * * /usr/bin/flock -w 0 $HOME/.cron.lock drush --quiet --root=$HOME/httpdocs --uri=http://www.example.org cron
In an upcoming blog post I’ll explain why running a full cron every minute is a bad idea.