An exhibition of data visualisations through the ages at the British Library  contained some visually stunning examples of ways of presenting scientific data. There were some classic examples, including Florence Nightingales polar area diagrams revealing higher deaths from unclean hospitals than deaths on the Crimean battlefield in 1858  and John Snows maps plotting the 1854 cholera outbreak in Soho, London . Martin Krzywinskis 2013 circular diagrams, on the other hand, map human to animal DNA for each chromosome; we have a lot in common with the platypus .
But there was also a rather plain looking pamphlet: Natural and Political OBSERVATIONS mentioned in a following INDEX, and made upon the Bills of Mortality . Published in 1662, John Graunts analysis of the records of deaths (burials) and births (christenings) in London collected weekly by parish clerks was a seminal piece of statistical work and looks rather like a spreadsheet but one drawn by hand using a quill pen. Pulling together the hundreds of weekly records over decades enabled Graunt to pick out trends, to offer explanations for differences in mortality between areas of London and, for example, to establish that around a third of all deaths each year in the early/mid 1600s were of children aged under six.
A haberdasher by profession, Graunt notes in his publication some self-deprecatory words to the effect that he hopes the data he presents makes a real difference to the world and that he recognises others may find errors (For herein I have, like a silly Scholeboy, coming to say my Lesson to the World (that Peevish, and Tetchie Master) brought a bundle of Rods wherewith to be whipt, for every mistake I have committed.). Not to be too peevish or tetchie, in translating Graunts table of deaths (casualties) from a web-based version  to a spreadsheet, it was clear that some of his totals were wrong. These are corrected in the figures. However, the arithmetic mistakes are probably less significant than problems with the raw data.
Graunt was well aware of the basic problems with the accuracy of data he collated. Ascertaining the cause of death can be difficult for an experienced physician, but those who collected the data were not doctors nor necessarily had access to professional advice. Many deaths too would have simply gone unreported. And using christenings as equivalent to births was problematic as religious views changed over time (see figure 4). Nevertheless, he was circumspect where there were significant problems with the data, and he was able to bust a few common myths of the time that Londons population must number in the millions (in fact more like 400,000) or that peoples fears of certain diseases were out of proportion with the actual numbers of deaths from these causes.
So what kind of illnesses and diseases did people die of in 17th century London? Canker, Sore mouth and Thrush not a Dickensian firm of solicitors - was, thankfully, a minor cause of death (figure 1); Wolf accounted for eight deaths in 1650 and leaves a gaping hole of a back story to be told; Kings Evil or scrofula, a tubercular infection of the throat lymph glands and named on the belief that the cure was a touch from a monarch - accounted for an average of around 30 deaths a year between 1629 and 1660. There were a low number of deaths from execution too although a spike around the time of the last phase of the English Civil war in 1650 (figure 2).
Figure 1: Causes of death (burials): London: 1655-1658
Figure 2: Trends in deaths from executions: London: 1629-1636 and 1647-1660.
But, aside from those years when there were plague epidemics, the main killers were Consumption and cough, Chrisomes and infants and Ague and fever (figures 1 and 3). So, a combination of tuberculosis (plus other wasting illnesses), infant mortality and a set of feverish symptoms that probably covered quite a range of distinct diseases. However, when it happened, the impact of a plague epidemic was dramatic (figure 4).Figure 3: Trends in top three causes of death: London: 1629-1636 and 1647-1660.
Figure 4: Christenings and deaths from plague and non-plague causes: London, 1604-1661
Three hundred and fifty years ago, accurate and consistent classification of deaths was a problem for Graunt. But even today, while we have systematised causes of death and disease (eg ICD-10; the international classification of causes of death and diseases: Bubonic plague (A20.0) has six subcategories and there is a code (Y35.5) for Legal execution ), there remains a degree of imprecision which, in many developing countries for example, means that even the most basic of health statistics deaths often remain subject to estimate rather than record 
In 1674 Graunt died, aged 53, contributing one more statistic to the burial record that year (for jaundice).
2. Nightingale F (1858) Diagram of the Causes of Mortality in the Army of the East. Notes on matters, affecting the health, efficiency and hospital administration of the British Army. London, http://pressandpolicy.bl.uk/imagelibrary/detail.aspx?MediaDetailsID=2147
3. Snow J (1855) On the Mode of Communication of Cholera, 2nd Ed, John Churchill, London, England, 1855. http://www.ph.ucla.edu/epi/snow/snowbook.html
4. Krzywinski M (2013) Circles of Life. (Full image) http://www.wired.com/images_blogs/wiredscience/2014/02/circles-of-life.png
5. Graunt J (1662) Natural and Political OBSERVATIONS mentioned in a following INDEX, and made upon the Bills of Mortality http://www.edstephan.org/Graunt/bills.html
6. WHO (2014) International Classification of Diseases http://www.who.int/classifications/icd/en/
7. WHO/UNICEF/UNFPA/World Bank (2012) Trends in Maternal Mortality: 1990 to 2010: WHO, UNICEF, UNFPA and The World Bank estimates. WHO, Switzerland. http://whqlibdoc.who.int/publications/2012/9789241503631_eng.pdf)