in the book of «esbath-ul-wasiyah», ali-ibn-hussein-ibn-ali masoudi says:
verily, right from the time of amir-ul-mumineen ali (a.s.) till the period of imam ali an-naqi (a.s.) and imam hassan askari (a.s.) it was customary for the shias to meet their imam whenever they wished. if they were deprived of this bounty all at once then doubt and hesitation would have overtaken them. rather the faith of some of them would have become shaky. thus imam ali an-naqi (a.s.) and imam askari (a.s.) adopted this path as mentioned by masoudi so that the shias would gradually and gradually become
acquainted with imam's concealment.
imam ali an-naqi (a.s.) and imam hassan askari (a.s.) took up this excellent path for this very reason. strict alertness of the rulers who were contemporary to the afore-mentioned two imams confirm this matter. this resulted in fewer meetings and contacts with them especially so in the case of well-known shii'tes.
the apparent glory and magnificience of the afore-said two imams (a.s.) and the great number of servants and slaves and their greatness and eminence (which would naturally become the cause of fewer meetings of the common shias and rather their special shias except at fixed and special times) too confirms the matter of occultation.
later on, the policy of bani-abbass changed with regards to the twelve imams and their policy demanded respect and honour of the imams and this path was first put into practice by ma'mun abbassid.
those who cast a glance over history of hazrat ali-ibn-musa ar-ridha imam muhammad taqi, imam ali an-naqi and imam hassan askari will realize the way of association of the caliphs with imams. this is because they believed in the greatness and magnificience of imams (a.s.) and had kept at their disposal house, goods, feather, dress, servants, slaves and wealth for such motives which they had in mind. the main motive of the caliphs, as per their own imagination was to receive more ease and attention when in the company of the the imam especially so in the case of the afore-said two imams.
the reason why imam ali an-naqi concealed himself from the views of the shias on much lesser occasions than imam hassan askari (a.s.) was that there was to be two occultation for our master Mahdi - one was the minor occultation during which period the deputies and special representatives of Mahdi (a.s.) were having access to hazrat until the time when the shias became familiar with the absence and concealment of imam (a.s.) and the period of major occultation started wherein the special deputyship was cut off and unlike the shias who had the privilege of meeting hazrat's great fathers, none have the opportunity of meeting the imam officially.