All this recent food discussion had me digging up information from the very informative book by K.T. Achaya, "Indian food - a historical companion".
Idli : The first mention of idli in literature seems to be "iddalige" in the Vaddaradhane, a work in Kannada in the year AD 920, where it figures as one of the eighteen items seved to a brahmachari who visits the home of a lady. There are some other references in the literature but in all of them, upto 1250 AD, three elements of modern idli-making are missing :the use of grits along with urad daal, the long fermentation of the mix and the steaming of the batter to fluffiness. There is also a suggestion by Achaya that the origin of modern idli may have been Indonesia. The Indonesians have a product very similar to the idli, called the kedli and the cooks of the Hindu kings of Indonesia, during their visits home (often to look for brides) between the eighth and twelfth century brought the innocative fermentation technique to South India.
Dosai: Tamil Sangam literature in the 6th century AD mentions the dosai but not the idli, which only appears in Kannada literature four centuries later. The Manasollasa written in the twelfth century AD in Sanskrit mentions the dhosaka, for which only pulses, and no rice were used.
Chilli: There is no mention whatsoever of the chilli in Indian literature before the sixteenth century AD. In AD 1563 the meticulous book of Garcia da Orta, the doctor-botanist does not record it, and in AD 1590, not a single recipe of the fifty or more given in the Ain-i-Akbari uses anything other than pepper to achieve pungency. The chilli must have entered India soon after the voyages of Vasco Da Gama. The great south Indian composer Purandaradasa (AD 1480-1564) sang of the chili - "I saw you green, then turning redder as you ripened, nice to look at and tasty in a dish, but too hot if an excess is used. Savior of the poor, enhancer of good food, even to think of (the deity) Panduranga Vittala is difficult"".
Vada: Termed 'vataka', the vada is fully described even in the Dharma Sutras (800-300BC) as soaked, coarsely ground and fermented pulses, fashioned into various shapes and deep-fried in ghee. Patanjali (2 BC) also has a reference. the first reference to dahi-vada appears in Apabrahmasatrayi, where it mentions vatakas of several kind dipped in milk and curd.
Coffee: The first mention in writing in the Indian context is by Edward Terry, 1618 AD, using an anglicization of an Arabic word: 'Many of the people who are strict about their religion use no wine at all. They use a liquor more healthful than pleasant which they call cohha: a black seed boiled in water, which little alters the taste of the water. Notwithstanding, it is very good to help digestion, to quicken the spirits and cleanse the blood." Sixty years later, Jean de Thevenot remarked that in Sindh the brahmins drank nothing but 'water wherein they put coffee and tea.' Coffee was brought to India by the Arab traders. Coffee plants originated in Ethiopia and went to Yemen in Saudi Arabia.
So, a full South Indian breakfast could have been had circa 1625 :-)