The Sun is nowadays observed using different techniques that provide an almost instantaneous 3-D map of its structure. Of particular interest is the study of the variability in the solar output produced by the dissipation of m- netic energy on different spatial and temporal scales – the so-called magnetic activity. The 11-year cycle is the main feature describing this phenomenon. Apart from its intrinsic scientific interest, this topic is worth studying because of the interaction of such processes with the terrestrial environment. A fleet of space and ground-based observatories are currently monitoring the behaviour of our star on a daily basis. However, solar activity varies not only on this decadal time-scale, as has been attested mainly through two methods: (a) records of the number of sunspots observed on the solar surface from 1610, and (b) the records of 14 10 cosmogenic isotopes, such as Cand Be, measured in tree-rings and i- cores, respectively. The study of the long-term behaviour of solar activity may be comp- mented by the study of historical accounts describing phenomena directly or indirectly related to solar activity. Numerous scientific and non-scientific d- uments have reported these events and we can make use of them as a proxy of solar activity in past times.