Here is Mrs Beeton’s idea of a table spoonful:
A TABLE-SPOONFUL is frequently mentioned in a recipe, in the prescriptions of medical men, and also in medical, chemical, and gastronomical works. By it is generally meant and understood a measure or bulk equal to that which would be produced by half an ounce of water.
15 ml for those in the know – although there is a slight discrepancy between US fluid ounces and Imperial fluid ounces.