The Rat King, 1576
This is the earliest known illustration of what have been called 'Rat Kings', a grouping of rats with their tails tangled together. This illustration is from Emblemata et aliqvot nvmmi antiqvi operis, by Joannes Sambucus, appearing in the fourth edition in 1576.
This copy of the image comes from an online edition of the book at the Google Books website [Link Here].