What makes this particular heart so significant is the fact that it stands in the position of a 15th century Tolbooth which was a prison as well as a site of public execution before it was demolished in 1917.
As it was a prison, one can imagine it was not a very popular place, particularly amongst the people of Edinburgh, and this is how spitting on the heart came to be. It is now said to be good-luck to spit on the heart, but it was originally done as a sign of contempt for the former prison. Criminals as well as locals would express their dislike of the tollbooth by spitting on the heart. It has also be said that because of the spot where the heart lays, it is directly outside the prison, and many debtors may have spit on this heart upon their release.
The tradition still goes on to this day. Usually spitting in public is discouraged, but in Edinburgh it's a tradition! By simply taking a wee walk up the Royal Mile, you are sure to witness many people spitting on the heart. Some do it for good luck while some locals of Edinburgh may spit on the heart when they are feeling angry by politics or local policy.
Spitting in the heart can also be seen as a sign of aversion to a well-known Scottish football team. Heart of Midlothian Football Club, also commonly known as Hearts is a Scottish football club based in Gorgie in the west of Edinburgh. It is one of two Scottish Championship clubs in Edinburgh, the other being their Edinburgh derby rivals Hibernian FC.
The crest of the Edinburgh football team Heart of Midlothian is based upon this mosaic heart. There is a traditional local rivalry in Edinburgh between Hearts and Hibs with the Edinburgh derby match between the two clubs being one of the oldest rivalries in world football. That is why you will hear of, and may even have seen, many Hibs fans spitting in the heart as a sign of rivalry between the two clubs.
This site of the previous tollbooth features in the iconic Sir Walter Scott’s novel, also called The Heart of Midlothian, published in 1818. The book takes place during a time of unrest in Edinburgh when a mob stormed the Tolbooth and murdered one of its occupants. This book is a classic and often said to be one of Sir Walter Scott’s best ensuring this heart will never be forgotten.
So if you are visiting Edinburgh as a tourist, please do not be afraid to spit on this famous heart. It is said to bring good luck and legend has it that if you do spit on the heart, you are destined to return back to Edinburgh!