Baedeker advises on tipping at the Blue Grotto

Found in an 1889 edition of Badeker's Southern Italy this description of the Blue Grotto at Capri:

Blue Grotto. — A visit to the Blue Grotto from the Marina at Capri, where suitable light boats will be found, occupies 1 3/4 to 2hrs. The best light is between 10 and 12 o'clock. The authorised fare for the trip (there and back) is 1 1/4 fr. for each person, but almost no boatman will undertake it without an additional fee of 1-2 fr. The skiffs are not allowed to take more than three passengers. If the wind blows strongly from 

the E. or N. access to the grotto is impossible.The Blue Grotto is situated on the N. side of the island, about l 1/4 m. from the landing-place of Capri. 

The row along the base of the precipitous rocky shore is exceedingly beautiful. The sea swarms with gaily coloured sea-stars and jelly-fish, many of which float on the surface of the water. In 1/4 hr - we reach the ruins of the Baths of Tiberius, where a fragment of an ancient wall and part of a column in the water are to be seen, and in 1/2 hr. more we arrive at the entrance of the **Blue Grotto (Grotta Azzurra), which is scarcely 3 ft. in height. Visitors must lie down in the boat on entering. In the interior the roof rises to a height of 41 ft.;the water is 8 fathoms deep. Length of the grotto 175 ft., greatest width 100 ft. The effect of the blue refraction of the light on every object is indescribable, and at first completely dazzles the eye. Objects in the water assume a beautiful silvery appearance. 

One of the boatmen usually offers to bathe in order to show this effect, and is sufficiently rewarded with 1 fr., although he generally makes the exorbitant demand of 2-3 fr...The grotto, which was known to the ancients, fell into oblivion in the middle ages, but since 1822, when it was re-discovered by fishermen, it has justly been a favourite attraction. 

Baedeker occasionally advises on tipping in this way. In the edition of 1909 (22 years later) the suggested tip is still I franc but to a swimming boy. It also explains the beautiful light:

 The wonderful blue colour arises from the fact that the light penetrates through the medium of the water. The effect is therefore most striking in bright summer weather about midday.  Objects in the water assume a silvery appearance. A boy offers to bathe to show this effect ( 1Fr. at most,even for a party), but the visitor's own hand or arm may serve the purpose. 

Baedeker's give occasional hints on tipping and also methods of dealing with beggars:

Begging still continues to be one of those national nuisances to which the traveller must habituate himself. The best mode of get- ting rid of importunate applicants is to bestow a donation of 2c. or at most 5 c., or else firmly to decline giving with — niente, or a gesture of disapproval. — The misplaced generosity of some travellers, especially to children, has encouraged a habitual importunity that seriously interferes with the enjoyment of the beauty of the country, especially in the neighbourhood of Naples and in some parts of Sicily. Still more reprehensible than the bestowal of an occasional gratuity upon children, is the foolish practice of 'scattering' copper coins to be struggled for by the Street Arabs, etc.  

In the 1909 edition they simply state (under 'Mendicancy')- 'Money should never be given to children.'